In-situ growth of perovskite quantum dots on raspberry-like TiO2 hollow spheres and the resulting product

Abstract

The application discloses a method for in-situ growth of perovskite quantum dots on raspberry-like TiO2 hollow spheres and a product obtained by the method. Hollow carbon spheres are uniformly dispersed in an ethanol solution, and an alcohol salt of titanium is added dropwise into the suspension in batches. After each drop, the reaction is kept for a certain time, and finally the sample is separated. The perovskite quantum dot precursor and the obtained sample are uniformly mixed by grinding, and then subjected to microwave treatment. The obtained pretreated mixed sample is calcined in air to obtain raspberry-like TiO2 hollow spheres loaded with perovskite quantum dots. The perovskite quantum dots are synthesized by high-temperature solid-phase synthesis without adding ligands, and the quantum dots have good crystallinity. The interface between the quantum dots and the TiO2 phase develops well and has few defects, which is beneficial to carrier separation and transmission. The deposition of the quantum dots improves the specific surface area of the TiO2 material, and the photocatalytic performance of the TiO2 material is significantly improved. The obtained composite material has important applications in the fields of hydrogen production by water photolysis, CO2 photocatalytic reduction, hydrogen peroxide production by photocatalysis, chemical fuel conversion and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for in-situ high-temperature growth of perovskite quantum dots on raspberry-like TiO2 hollow spheres and the resulting product, which can also be referred to as a high-temperature synthesis technique for a perovskite quantum dot / raspberry-like TiO2 hollow sphere heterojunction composite photocatalytic material and the resulting product, and belongs to the field of green energy materials and application technologies. BACKGROUND

[0002] Anatase TiO2 is a typical photocatalyst material and is widely used in the field of environment. Since Japanese scientists discovered the application of TiO2 in the field of water photolysis in 1972, scientists have begun to pay close attention to the research in this field and have expanded it to various fields of photocatalytic application. TiO2 is widely used because it does not contain heavy metal elements, is non-toxic, environmentally friendly, inexpensive, and has a simple preparation process. The main disadvantage of TiO2 photocatalyst is that its absorption is in the ultraviolet region, and the utilization rate of sunlight is not high. In order to improve its photocatalytic efficiency, expand the light response, and improve the separation and transmission efficiency of photo-generated carriers, it is crucial. TiO2 has rich morphological characteristics, so forming a heterojunction with other semiconductor materials to improve the photocatalytic efficiency has become a new focus.

[0003] Perovskite quantum dots are a typical semiconductor luminescent material, and their light absorption can cover the entire visible light region. The process of luminescence is exactly the opposite of photocatalysis. Luminescence is the emission of photons through the recombination of photo-generated electrons and holes, while the photocatalytic process is the separation of photo-generated electrons and holes. These photo-generated electrons and holes participate in the photocatalytic redox reaction, so the luminescence phenomenon will disappear. Due to the excellent absorption properties of perovskite quantum dots, their application in the field of photocatalysis is obvious. The key is to prevent the recombination of photo-generated electrons and holes. On the other hand, in order to obtain high-quality perovskite quantum dots, traditional solution chemical methods usually require the addition of organic ligands to passivate the surface, and these ligands will affect the migration of photo-generated electrons, so perovskite quantum dots are used to form a heterojunction with a photocatalyst to obtain high-quality hydrophilic nanoparticles under ligand-free conditions, and the interface is well developed. SUMMARY

[0004] In view of the fact that the existing synthesis technology of perovskite quantum dots is difficult to be directly applied in the field of photocatalysis, the present application provides an in-situ growth method of perovskite quantum dots on raspberry-like TiO2 hollow spheres. This method controls the reaction process to synthesize ligand-free perovskite quantum dots in-situ at high temperature on raspberry-like TiO2 hollow spheres. Finally, high-quality perovskite quantum dots are directly embedded in raspberry-like hollow TiO2 spheres in-situ, and a heterojunction with excellent interface properties is obtained. This method is simple, reproducible, and suitable for industrial production. The prepared perovskite quantum dots are uniformly embedded on the raspberry-like hollow TiO2 spheres, have good stability, and have good application prospects.

[0005] The specific technical solutions of the present application are as follows:

[0006] A method for in-situ growth of perovskite quantum dots on raspberry-like TiO2 hollow spheres, the in-situ growth refers to solid-phase in-situ high-temperature growth, the method comprises the following steps:

[0007] (1) uniformly disperse the hollow carbon spheres into ethanol to obtain a suspension, add the titanium alkoxide into the suspension dropwise for 3-8 times, keep the reaction after each drop, and finally separate the sample;

[0008] (2) uniformly mix the perovskite quantum dot precursor and the sample obtained in step (1) by grinding, and then perform microwave treatment to obtain a pretreated mixed sample;

[0009] (3) calcine the pretreated mixed sample in air to obtain raspberry-like TiO2 hollow spheres loaded with perovskite quantum dots.

[0010] Further, in step (1), the hollow carbon spheres are carbon spheres with a spherical outer surface and a hollow interior, and the size of the hollow carbon spheres is less than or equal to 200 nm, for example, 50 nm, 100 nm, 150 nm, or 200 nm.

[0011] Further, in step (1), the hollow carbon spheres are first uniformly dispersed in ethanol, and in order to improve the dispersion effect, ultrasonic dispersion can be performed for a certain period of time. The reaction medium is pure ethanol. The mass-volume ratio of the hollow carbon spheres to ethanol is 0.5-0.8 g: 10 ml, for example, 0.5 g: 10 ml, 0.6 g: 10 ml, 0.7 g: 10 ml, or 0.8 g: 10 ml.

[0012] Further, in step (1), the titanium alkoxide is at least one of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, and tetrabutyl titanate. The mass ratio of the titanium alkoxide to the hollow carbon spheres is preferably 5-10: 1, for example, 5: 1, 6: 1, 7: 1, 8: 1, 9: 1, or 10: 1.

[0013] Further, in step (1), the titanium alkoxide is added in batches by dropwise addition, preferably in 3-8 times, such as 3 times, 4 times, 5 times, 6 times, 7 times, 8 times. Each time the titanium alkoxide is added at a dropwise addition rate of 0.05-0.1 mL / min, such as 0.05 mL / min, 0.06 mL / min, 0.07 mL / min, 0.08 mL / min, 0.09 mL / min, 0.1 mL / min. After each dropwise addition, the reaction is incubated for 1-2 h at room temperature. For example, when the titanium alkoxide is added in three times, first, a portion of the titanium alkoxide is added at a rate of 0.05-0.1 mL / min, and after the dropwise addition, the reaction is incubated for 1-2 h; then, another portion of the titanium alkoxide is added at a rate of 0.05-0.1 mL / min, and after the dropwise addition, the reaction is incubated for 1-2 h; finally, the remaining titanium alkoxide is added at a rate of 0.05-0.1 mL / min, and after the dropwise addition, the reaction is incubated for 1-2 h.

[0014] Further, in step (1), the titanium alkoxide is added in batches by dropwise addition, preferably in 3-8 times, such as 3 times, 4 times, 5 times, 6 times, 7 times, 8 times. Each time the titanium alkoxide is added at a dropwise addition rate of 0.05-0.1 mL / min, such as 0.05 mL / min, 0.06 mL / min, 0.07 mL / min, 0.08 mL / min, 0.09 mL / min, 0.1 mL / min. After each dropwise addition, the reaction is incubated for 1-2 h at room temperature. For example, when the titanium alkoxide is added in three times, first, a portion of the titanium alkoxide is added at a rate of 0.05-0.1 mL / min, and after the dropwise addition, the reaction is incubated for 1-2 h; then, another portion of the titanium alkoxide is added at a rate of 0.05-0.1 mL / min, and after the dropwise addition, the reaction is incubated for 1-2 h; finally, the remaining titanium alkoxide is added at a rate of 0.05-0.1 mL / min, and after the dropwise addition, the reaction is incubated for 1-2 h.

[0015] Further, in step (2), the perovskite quantum dot has a structure formula of CsPbX3, wherein X is a halogen, such as chlorine, bromine, iodine, etc. The perovskite quantum dot precursor is a mixture of cesium halide and lead halide, and the cesium halide can be cesium chloride, cesium bromide, cesium iodide, etc., and the lead halide can be lead chloride, lead bromide, lead iodide, etc.

[0016] Further, in step (2), the amounts of the perovskite quantum dot precursors (cesium halide and lead halide) are added according to the stoichiometric ratio of the perovskite quantum dot molecular formula.

[0017] Further, in step (2), the total amount of the perovskite quantum dot precursors (cesium halide and lead halide) is 10-20 wt% of the sample obtained in step (1), such as 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%.

[0018] Further, in step (2), the perovskite quantum dot precursors can be ground first, mixed uniformly, and then mixed with the sample obtained in step (1) for grinding.

[0019] Further, in step (2), the temperature of the microwave treatment is 70-90℃, for example 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 88℃, 88℃, 89℃, 90℃. The treatment time is 0.5-3 hours, for example 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours.

[0020] Further, in step (3), the pre-treated mixed sample is calcined in air, which can remove the carbon component and complete the synthesis of quantum dots at the same time, the perovskite quantum dots are embedded on the surface and gap of the raspberry-like hollow carbon spheres, realizing the combination of raspberry-like TiO2 hollow spheres and quantum dots.

[0021] Further, in step (3), the calcination temperature is 400-500℃, for example 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃. The calcination time is 0.5-2 hours, for example 0.5 hours, 1 hour, 1.5 hours, 2 hours.

[0022] Further, in step (3), after calcination, the sample is washed with water to remove unreacted chemicals, then washed with ethanol, centrifuged to obtain raspberry-like TiO2 hollow spheres loaded with perovskite quantum dots, which can also be called perovskite quantum dot / raspberry-like TiO2 hollow sphere heterojunction composite material.

[0023] The application also provides raspberry-like TiO2 hollow spheres loaded with perovskite quantum dots prepared according to the above method, which is a perovskite quantum dot / raspberry-like TiO2 hollow sphere heterojunction composite material. The composite material of the application has good response in the ultraviolet-visible light range, the quantum dots have good crystallinity, the interface between the quantum dots and the TiO2 phase develops well and has few defects, which is beneficial to carrier separation and transmission. It is a high-efficiency photocatalyst with ultraviolet-visible light response. The deposition of quantum dots increases the specific surface area of TiO2 material, and the photocatalytic performance is significantly improved. The composite material has important applications in the fields of hydrogen production by water splitting, CO2 photocatalytic reduction, hydrogen peroxide production by photocatalysis, and chemical fuel conversion.

[0024] The application has the following beneficial effects:

[0025] 1. This invention controls the deposition of titanium raw materials on hollow carbon spheres by controlling the reaction process, uses low-temperature microwave treatment to make quantum dot raw materials fully and uniformly dispersed in TiO2 layer, and finally uses high-temperature carbon component removal process to achieve quantum dot growth. The carbon component removal process can prevent the oxidation of quantum dots, and finally high-quality quantum dots are directly embedded in situ into raspberry-shaped hollow TiO2 spheres to obtain heterojunctions with excellent interface properties.

[0026] 2. The perovskite quantum dot synthesis process of this invention is completed under high-temperature solid-state conditions, eliminating the need for ligands and thus removing the influence of ligands on photogenerated carriers. The quantum dots exhibit good crystallinity and have few defects at the interface between the quantum dots and TiO2, thereby ensuring carrier transport efficiency and ensuring that the light absorption range of the final composite material is tunable.

[0027] 3. The perovskite quantum dots of this invention have an tunable absorption range, which can extend the light absorption of the composite material to the entire visible light range. This extended photoresponse improves the utilization rate of sunlight, resulting in a photocatalyst with excellent performance. This composite material has important applications in fields such as photocatalytic water splitting for hydrogen production, photocatalytic reduction of CO2, photocatalytic hydrogen peroxide production, and chemical fuel conversion.

[0028] 4. The preparation method of this invention is simple, easy to implement, does not use organic solvents, has low manufacturing cost, and has good application prospects. Attached Figure Description

[0029] Figure 1 This is an electron microscope image of the sample obtained in Example 1.

[0030] Figure 2 This is a high-magnification electron microscope image of the sample obtained in Example 1.

[0031] Figure 3 The figure shows the experimental results of the photocatalytic CO2 reduction to methanation of the sample obtained in Example 1. Detailed Implementation

[0032] The present invention will be further illustrated by the following embodiments. The following description is only for explaining the present invention and does not limit its content.

[0033] In the following examples, the hollow carbon spheres used were purchased from Nanjing Jicang Nanotechnology Co., Ltd., and their size was 100-200nm.

[0034] Example 1

[0035] 1.1 Disperse 0.56 g hollow carbon spheres into 10 mL ethanol, and obtain a uniform suspension after ultrasonic treatment for 0.5 h. Add 3.9 g tetrabutyl titanate dropwise into the suspension at a rate of 0.08 mL / min in 5 portions, and react for 1.5 h after each dropwise addition. Repeat the dropwise addition, and react for 1.5 h after the last dropwise addition of tetrabutyl titanate. Then, centrifuge the sample and reserve it for use.

[0036] 1.2 Mix 0.16 g lead bromide and 0.10 g cesium bromide with 1.73 g of the sample obtained in step 1.1, and grind to obtain a uniform mixture. Then, use a microwave reactor to treat the mixture at 80 °C for 1.8 h, and obtain a pretreated mixture.

[0037] 1.3 Treat the mixture obtained in step 1.2 at 450 °C for 1 h under air, remove the carbon component, complete the synthesis of quantum dots, and realize the compounding of raspberry-shaped TiO2 hollow spheres and quantum dots. Wash the obtained sample with water to remove unreacted chemical reagents, then wash with ethanol, centrifuge, and obtain raspberry-shaped TiO2 hollow spheres loaded with CsPbBr3 quantum dots.

[0038] Figure 1 and Figure 2 The obtained product is shown in the electron microscope photograph, and it can be seen from the photograph that the CsPbBr3 quantum dots are uniformly distributed in the TiO2 hollow spheres. The sample exhibits good photocatalytic CO2 reduction properties and good stability.

[0039] Example 2

[0040] 2.1 Disperse 0.56 g hollow carbon spheres into 10 mL ethanol, and obtain a uniform suspension after ultrasonic treatment for 0.5 h. Add 4 g tetramethyl titanate dropwise into the suspension at a rate of 0.05 mL / min in 8 portions, and react for 1 h after each dropwise addition. Repeat the dropwise addition, and react for 1 h after the last dropwise addition of tetramethyl titanate. Then, centrifuge the sample and reserve it for use.

[0041] 2.2 Mix 0.16 g lead bromide and 0.10 g cesium bromide with 2.61 g of the sample obtained in step 2.1, and grind to obtain a uniform mixture. Then, use a microwave reactor to treat the mixture at 90 °C for 1 h, and obtain a pretreated mixture.

[0042] 2.3 The mixed sample obtained in step 2.2 is treated at 400 degrees Celsius for 2 hours under air condition to remove the carbon component, complete the synthesis of quantum dots, and realize the compounding of raspberry-like TiO2 hollow spheres and quantum dots. The obtained sample is washed with water to remove unreacted chemical reagents, then washed with ethanol, centrifuged, and raspberry-like TiO2 hollow spheres loaded with CsPbBr3 quantum dots are obtained. The morphology of the obtained sample is similar to that of Example 1.

[0043] Example 3

[0044] 3.1 0.7 grams of hollow carbon spheres are uniformly dispersed in 10 mL of ethanol, and after ultrasonic treatment for 0.5 hours, a uniform suspension is obtained. Tetraethyl titanate 6.5 grams is added dropwise to the suspension at a rate of 0.10 mL / min in 6 times, and after each dropwise addition is completed, the reaction is carried out for 2 hours, and the next dropwise addition is carried out. After the completion of the last dropwise addition of tetraethyl titanate, the reaction is carried out for 2 hours, and then the sample is centrifuged and prepared for use.

[0045] 3.2 Lead bromide 0.16 g and cesium bromide 0.10 g are uniformly ground, mixed with 2.61 grams of the sample obtained in step 3.1, and ground to obtain a uniform mixture. Then, a microwave reactor is used to treat the mixture at 70 degrees Celsius for 3.0 hours to obtain a pretreated mixed sample.

[0046] 3.3 The mixed sample obtained in step 3.2 is treated at 500 degrees Celsius for 0.5 hours under air condition to remove the carbon component, complete the synthesis of quantum dots, and realize the compounding of raspberry-like TiO2 hollow spheres and quantum dots. The obtained sample is washed with water to remove unreacted chemical reagents, then washed with ethanol, centrifuged, and raspberry-like TiO2 hollow spheres loaded with CsPbBr3 quantum dots are obtained. The morphology of the obtained sample is similar to that of Example 1.

[0047] Example 4

[0048] 4.1 0.6 grams of hollow carbon spheres are uniformly dispersed in 10 mL of ethanol, and after ultrasonic treatment for 0.5 hours, a uniform suspension is obtained. Tetraethyl titanate 4.2 grams is added dropwise to the suspension at a rate of 0.08 mL / min in 5 times, and after each dropwise addition is completed, the reaction is carried out for 1.5 hours, and the next dropwise addition is carried out. After the completion of the last dropwise addition of tetraethyl titanate, the reaction is carried out for 1.5 hours, and then the sample is centrifuged and prepared for use.

[0049] 4.2 Lead chloride 0.086 g and cesium chloride 0.05 g are uniformly ground, mixed with 1.36 grams of the sample obtained in step 4.1, and ground to obtain a uniform mixture. Then, a microwave reactor is used to treat the mixture at 90 degrees Celsius for 0.5 hours to obtain a pretreated mixed sample.

[0050] 4.3 The mixed sample obtained in step 4.2 was treated at 450 degrees Celsius for 1 hour under air condition to remove the carbon component, complete the synthesis of quantum dots, and realize the compounding of raspberry-shaped TiO2 hollow spheres and quantum dots. The obtained sample was washed with water to remove unreacted chemical reagents, then washed with ethanol, centrifuged, and raspberry-shaped TiO2 hollow spheres loaded with CsPbCl3 quantum dots were obtained. The morphology of the obtained sample was similar to that of Example 1.

[0051] Example 5

[0052] 5.1 Hollow carbon spheres 0.8 g were uniformly dispersed in 10 mL of ethanol, and a uniform suspension was obtained after ultrasonic treatment for 0.5 hours. Tetrapropyl titanate 5.6 g was added dropwise to the suspension at a rate of 0.08 mL / min in 7 times, and after each dropwise addition was completed, the reaction was carried out for 1.5 hours before the next dropwise addition. After the completion of the last dropwise addition of tetrapropyl titanate, the reaction was carried out for 1.5 hours, and then the sample was centrifuged and reserved.

[0053] 5.2 Lead iodide 0.14 g and cesium iodide 0.078 g were added, uniformly ground, mixed with 1.09 g of the sample obtained in step 5.1, and uniformly ground to obtain a uniform mixture. Then, the mixture was treated in a microwave reactor at 75 degrees Celsius for 1.8 hours to obtain a pretreated mixed sample.

[0054] 5.3 The mixed sample obtained in step 5.2 was treated at 450 degrees Celsius for 1 hour under air condition to remove the carbon component, complete the synthesis of quantum dots, and realize the compounding of raspberry-shaped TiO2 hollow spheres and quantum dots. The obtained sample was washed with water to remove unreacted chemical reagents, then washed with ethanol, centrifuged, and raspberry-shaped TiO2 hollow spheres loaded with CsPbI3 quantum dots were obtained. The morphology of the obtained sample was similar to that of Example 1.

[0055] Comparative Example 1

[0056] 1.1 The same as Example 1.1;

[0057] 1.2 The same as Example 1.2, except that there was no microwave treatment process;

[0058] 1.3 The same as Example 1.3;

[0059] The obtained sample had uneven distribution of cesium bromide lead quantum dots, and had very poor photocatalytic properties.

[0060] Comparative Example 2

[0061] 2.1 The same as Example 2.1;

[0062] 2.2 The same as Example 2.2;

[0063] 2.3 The same as Example 2.3, except that the calcination temperature was 600 degrees Celsius;

[0064] The results show that the sample is black and has no photocatalytic properties.

[0065] Comparative Example 3

[0066] 3.1 Same as Example 3.1;

[0067] 3.2 Same as Example 3.2;

[0068] 3.3 Same as Example 3.3, except that the calcination is done in inert N2.

[0069] The results show that the sample is black and has no photocatalytic properties.

[0070] Comparative Example 4

[0071] 4.1 Same as Example 1.1;

[0072] 4.2 Same as Example 1.2, except that the microwave treatment temperature is 100 degrees Celsius and the treatment time is 1.8 hours;

[0073] 4.3 Same as Example 1.3;

[0074] The resulting sample of cesium bromide lead quantum dots is unevenly distributed and has poor photocatalytic properties.

[0075] Comparative Example 5

[0076] 5.1 0.56 grams of hollow carbon spheres were uniformly dispersed in 10 mL of ethanol, and after ultrasonic treatment for 0.5 hours, a uniform suspension was obtained. Tetraethyl titanate 3.9 grams was added dropwise to the suspension at a rate of 0.2 mL / min, and after the dropwise addition was complete, the reaction was carried out for 8 hours. Then the sample was centrifuged and reserved for use;

[0077] 5.2 Same as Example 1.2;

[0078] 5.3 Same as Example 1.3.

[0079] Photocatalytic property verification

[0080] 1. Experimental samples: samples prepared in the above examples and comparative examples, commercially available CsPbBr3 quantum dots, and raspberry-shaped TiO2 hollow spheres, the preparation method of the raspberry-shaped TiO2 hollow spheres being:

[0081] 1.1 0.56 grams of hollow carbon spheres were uniformly dispersed in 10 mL of ethanol, and after ultrasonic treatment for 0.5 hours, a uniform suspension was obtained. Tetraethyl titanate 3.9 grams was added dropwise to the suspension in 5 portions at a rate of 0.08 mL / min, and after each dropwise addition was complete, the reaction was carried out for 1.5 hours before the next dropwise addition was carried out. After the last dropwise addition of tetraethyl titanate was complete, the reaction was carried out for 1.5 hours, and then the sample was centrifuged and reserved for use.

[0082] 1.2 The sample obtained in step 1.1 is treated at 450 degrees Celsius for 1 hour under air condition, and the obtained sample is washed with water to remove unreacted chemical reagents, then washed with ethanol, centrifuged and separated to obtain raspberry-shaped TiO2 hollow spheres.

[0083] 2. Experimental steps: 20 mg of the experimental sample is uniformly mixed with 15 mL of deionized water to prepare a sample solution for CO2 photoreduction test. The sample solution is subjected to 15-minute high-purity CO2 bubbling and vacuum treatment, and then CO2 photoreduction measurement is performed under 420 nm LED light irradiation. The data is collected at a given time interval using a GC-7920 gas chromatograph, and the CH4 yield is obtained by dividing the number of moles of the obtained product CH4 by the reaction time and the mass of the added sample.

[0084] The experimental results are shown in Table 1 below.

[0085]

[0086] The stability experiment is performed using the photocatalyst of Example 1 as an example, and the experimental steps are as shown above. Each experiment is performed for 4 hours, and the experiment is repeated 5 times. The catalyst used in the first experiment is reused in the subsequent experiments. The experimental results are shown in Figure 3 As can be seen from the figure, the photocatalytic reduction capacity of the catalyst does not decrease after 5 experiments, indicating that the photocatalyst has good recyclable stability.

Claims

1. A method for in-situ growth of perovskite quantum dots on raspberry-shaped hollow TiO2 spheres, characterized in that: Includes the following steps: (1) Disperse hollow carbon spheres evenly in ethanol to obtain a suspension. Add titanium alkoxide to the suspension in 3-8 portions. Keep the temperature and react after each addition. Finally, separate the sample. (2) Grind and mix the perovskite quantum dot precursor and the sample obtained in step (1) evenly, and then microwave process them to obtain a pretreated mixed sample; (3) The pretreated mixed sample was calcined in air to obtain raspberry-shaped TiO2 hollow spheres loaded with perovskite quantum dots; In step (1), the titanium alkoxide is added at a rate of 0.05-0.1 mL / min, and the reaction is kept warm for 1-2 hours after each addition. In step (2), the perovskite quantum dot has the structural formula CsPbX3, where X is a halogen; the precursor of the perovskite quantum dot is a mixture of cesium halide and lead halide, and the amount of perovskite quantum dot precursor added is 10-20 wt% of the sample obtained in step (1); the microwave treatment temperature is 70-90℃, and the treatment time is 0.5-3 hours; In step (3), the calcination temperature is 400-500℃ and the calcination time is 0.5-2 hours.

2. The in-situ growth method according to claim 1, characterized in that: In step (1), the mass ratio of titanium alkoxide to hollow carbon spheres is 5-10:

1.

3. The in-situ growth method according to claim 1, characterized in that: In step (1), the titanium alkoxide is at least one of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate and tetrabutyl titanate.

4. The in-situ growth method according to claim 1, characterized in that: In step (1), the mass-to-volume ratio of hollow carbon spheres to ethanol is 0.5-0.8g:10ml.

5. Raspberry-shaped hollow TiO2 spheres loaded with perovskite quantum dots prepared by the in-situ growth method according to any one of claims 1-4.

6. The application of the raspberry-shaped TiO2 hollow spheres loaded with perovskite quantum dots as described in claim 5 as a photocatalyst.

7. The application of the raspberry-shaped TiO2 hollow spheres loaded with perovskite quantum dots as described in claim 5 in the photocatalytic reduction of CO2 to prepare methane.

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