A perovskite catalyst with adjustable vacancy defect density, preparation method and application thereof

Abstract

The present invention discloses a perovskite catalyst with adjustable vacancy defect density, a preparation method, and an application thereof, belonging to the technical field of perovskite materials. The present invention utilizes different metal halides, such as cesium bromide (CsBr) and lead bromide (PbBr2), cesium chloride (CsCl), sodium chloride (NaCl), and bismuth chloride (BiCl3), as well as a certain amount of organic solvent, as precursor materials, and obtains a perovskite catalyst with adjustable vacancy defect density by ball milling for a certain period of time. The defect density of the perovskite catalyst with adjustable vacancy defect density prepared by the present invention is inversely proportional to the polarity of the organic solvent. The preparation method is simple to operate, has a high success rate, and requires low equipment. It can significantly improve the utilization rate of photogenerated electrons and the catalytic activity of the perovskite catalyst. The method of the present invention points the way to improving the utilization rate of photogenerated carriers in metal halide perovskites.

Description

Technical Field

[0001] The present invention belongs to the field of perovskite materials, and in particular relates to a perovskite catalyst with adjustable vacancy defect density, a preparation method thereof, and an application thereof. Background Art

[0002] Solar energy is an inexhaustible clean energy source. Using artificial photosynthesis to convert solar energy into solar fuels is an effective approach to addressing current energy and environmental challenges. Photocatalytic technology utilizes semiconductors to absorb sunlight, generating photogenerated electrons and holes. These electrons and holes undergo charge transfer with reactive molecules adsorbed on the semiconductor surface, such as H₂O and CO₂, to catalyze the decomposition of water to produce hydrogen or the reduction of carbon dioxide to produce CO, CH₄, or other hydrocarbons. Photocatalytic CO₂ reduction has attracted considerable attention due to its potential to simultaneously achieve carbon reduction and clean energy conversion, and its advantages of simple architecture and ease of operation. The design and development of efficient catalysts has been a key focus in the field of photocatalytic CO₂ reduction research. Halide perovskites, as effective CO₂ reduction photocatalysts, offer advantages such as suitable conduction band positions, high extinction coefficients, low exciton binding energies, and easily tunable surface sites. These materials are expected to overcome the limitations of conventional oxides, sulfides, nitrides, and metal-organic frameworks in terms of light absorption, photogenerated electron utilization, redox activity, and catalytic stability, achieving superior photocatalytic CO₂ reduction performance.

[0003] For perovskite catalysts, vacancy defects significantly influence the behavior of photogenerated carriers and surface molecular reactions. Some vacancy defects are believed to capture photogenerated charges for surface catalysis, improving charge separation efficiency. However, some vacancy defects are considered deep-level defects, which also capture photogenerated charges but act as recombination centers, causing these captured charges to ultimately recombine non-radiatively, reducing charge separation efficiency. Furthermore, some vacancy defects can also affect the adsorption capacity of reactive molecules on the surface. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a perovskite catalyst with adjustable vacancy defect density and its preparation method and application, so as to solve the problems of low carrier utilization rate and uncontrollable regulation of vacancy defect density in the prior art perovskite catalyst, thereby controllably regulating the charge separation ability of the catalyst and the molecular reaction adsorption ability of the surface.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a perovskite catalyst with adjustable vacancy defect density comprises the following steps:

[0007] Step 1: Mixing a perovskite precursor powder and an organic reagent to obtain a perovskite precursor suspension; the perovskite precursor powder is prepared by mixing a halide of A and a metal compound; the metal compound is a metal compound of B, a metal compound of B', a metal compound of B'', or a metal compound of B'''; the halide of A and the anion in the metal compound are the same; the organic reagent is a non-polar reagent, a medium-level reagent, or a strong polar reagent;

[0008] Step 2, ball milling the perovskite precursor suspension to obtain a ball milled sample;

[0009] Step 3: drying the ball-milled sample and then calcining it to obtain a perovskite catalyst with adjustable vacancy defect density; as the polarity of the organic reagent increases, the defect density of the perovskite catalyst decreases.

[0010] A further improvement of the present invention is:

[0011] Preferably, in step 1, the halide of A is cesium chloride, cesium bromide, cesium iodide or cesium acetate.

[0012] Preferably, in step 1, the metal compound of B is lead chloride, lead bromide, zinc bromide, copper bromide, cobalt bromide, lead iodide or lead acetate; the metal compound of B' is sodium chloride, potassium chloride, copper chloride, silver chloride, sodium bromide, potassium bromide, copper bromide, silver bromide, sodium iodide, potassium iodide, copper iodide or silver iodide; the metal compound of B'' is bismuth trichloride, indium trichloride, antimony trichloride, bismuth tribromide, indium tribromide, antimony tribromide, bismuth triiodide, indium triiodide, antimony triiodide; the metal compound of B''' is tin tetrachloride, tin tetrabromide, tin tetraiodide and titanium tetrachloride, titanium tetrabromide or titanium tetraiodide.

[0013] Preferably, the non-polar reagent is cyclohexane, petroleum ether, hexane or pentane; the intermediate polar reagent is carbon tetrachloride, ethyl acetate, chloroform, dichloromethane, ether or toluene; and the strong polar reagent is acetic acid, acetonitrile, methanol, ethanol or isopropanol.

[0014] Preferably, in step 2, the ball milling speed is 500-1000 rpm, and the ball milling time is 2-5 h.

[0015] Preferably, in step 3, the drying temperature is 60 to 100 o C, drying time is 24 h.

[0016] Preferably, in step 3, the calcination temperature is 200 to 500 o C, calcination time is 2 to 5 hours

[0017] Preferably, in step 1, after adding the halide of A and the metal compound into the ball mill, an organic solvent is added into the ball mill.

[0018] A perovskite catalyst with adjustable vacancy defect density, wherein the perovskite catalyst is ABX3, A2B'B''X6 or A2B'''X6, wherein A is Cs; B is divalent Pb, Ge, Cu, Co, Zn or Sn; B' is monovalent Na, Cu, Ag or K; B'' is trivalent Bi, In, or Sb; B''' is tetravalent Sn or Ti; and X is Cl, Br or I.

[0019] Preferably, it is used for photothermal catalytic CO2 reduction or water decomposition to produce hydrogen.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention provides a method for preparing a perovskite catalyst with adjustable vacancy defect density. During the preparation process, a perovskite precursor powder is mixed with an organic solvent and wet ball milling is performed. The polarity of the solvent is changed to adjust the dissolution rate of the precursor halide salt, thereby changing the perovskite crystallization growth process, thereby preparing a perovskite catalyst with adjustable vacancy defect density. This method is based on the growth mechanism of halide perovskites and assists the dissolution and recrystallization of the precursor halide salt by adding a solvent. The preparation method is simple to operate, has a high success rate, and requires minimal equipment. It can significantly improve the utilization rate of photogenerated electrons and catalytic activity of perovskite catalysts. The method of the present invention points the way to improving the utilization rate of photogenerated carriers in metal halide perovskites.

[0022] The present invention also discloses a perovskite catalyst with adjustable vacancy defect density. The catalyst is ABX3, A2B'B''X6, or A2B'''X6. The catalyst is prepared by using precursor materials such as cesium salts, metal compounds, and organic reagents, and then high-speed ball milling of the precursors and high-temperature calcination of the resulting composite to obtain a perovskite catalyst with adjustable vacancy defect density, thereby promoting carrier separation and improving the utilization rate of photogenerated electrons. The catalyst has adjustable halide ion defect density and grain size, as well as high photothermal catalytic CO2 reduction activity. This preparation method points the way to defect control technology for metal halide perovskites and brings new opportunities for the development of metal halide perovskite photocatalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the operation flow of the method described in the example of the present invention.

[0024] Figure 2 This is a surface morphology of the catalyst prepared by the method described in the examples of the present invention.

[0025] Among them, (a) is acetonitrile; (b) is ethanol; (c) is carbon tetrachloride; (d) is ethane.

[0026] Figure 3 3 is a graph showing the relationship between the EPR signal intensity and the Br / Pb atomic ratio of the catalyst prepared by the method described in the examples of the present invention; wherein (a) is the EPR signal intensity; and (b) is the Br / Pb atomic ratio.

[0027] Figure 4 It is the normalized CO2 desorption peak area and the total CO2 reduction reaction electron number of the catalyst prepared by the method described in the example of the present invention; wherein, (a) figure is the normalized CO2 desorption peak area; (b) figure is the total CO2 reduction reaction electron number. DETAILED DESCRIPTION

[0028] The present invention is described in further detail below with reference to the accompanying drawings:

[0029] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention; the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance; in addition, unless otherwise expressly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be a communication between the internal parts of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] One embodiment of the present invention discloses a method for preparing a perovskite catalyst with adjustable vacancy defect density, see Figure 1 , the specific steps are as follows:

[0031] Step 1, selecting materials according to the chemical composition of ABX3, A2B'B''X6 or A2B'''X6 perovskite: the halide providing A is cesium chloride (CsCl), cesium bromide (CsBr), cesium iodide (CsI) or cesium acetate (CsCH3COO·xH2O); the metal compound providing B is lead chloride (PbCl2), lead bromide (PbBr2), zinc bromide (ZnBr2), copper bromide (CuBr2), cobalt bromide (CoBr2), lead iodide (PbI2) or lead acetate (Pb(CH3COO)2·xH2O); the metal compound providing B' is sodium chloride (NaCl), potassium chloride (KCl), copper chloride (CuCl), silver chloride (AgCl), sodium bromide (NaBr), potassium bromide (KBr), copper bromide (CuBr), silver bromide (AgBr), sodium iodide (NaI), potassium iodide (KI), copper iodide (CuI) or silver iodide (AgI); the metal compound providing B'' is bismuth trichloride (BiCl3), indium trichloride (InCl3), antimony trichloride (SbCl3), bismuth tribromide (BiBr3), indium tribromide (InBr3), antimony tribromide (SbBr3), bismuth triiodide (BiI3), indium triiodide (InI3), antimony triiodide (SbI3); the metal compound providing B''' is tin tetrachloride (SnCl4), tin tetrabromide (SnBr4), tin tetraiodide (SnI4) and titanium tetrachloride (TiCl4), titanium tetrabromide (TiBr4), titanium tetraiodide (TiI4).

[0032] Step 2: According to the stoichiometric ratio of ABX3, A2B'B''X6 or A2B'''X6 perovskite, weigh the halide containing A and place it in a ball mill with a metal compound that can provide B, B', B'' and B''' sources to obtain the corresponding perovskite precursor powder. Figure 1 As shown, during the ball milling process, CsBr and PbBr2 were partially dissolved in the added solvent and subsequently crystallized and grew into CsPbBr3.

[0033] Step 3: Select different organic reagents. The provided organic reagents include non-polar reagents, intermediate-polar reagents, and highly polar reagents. The non-polar reagents include cyclohexane, petroleum ether, hexane, and pentane; intermediate-polar reagents include carbon tetrachloride, ethyl acetate, chloroform, dichloromethane, diethyl ether, and toluene; and highly polar reagents include acetonitrile, acetic acid, methanol, ethanol, and isopropanol. The organic reagent is any of the above solvents. 3 to 30 ml of organic solvent is added based on the total mass of the precursor powder to obtain a precursor suspension. This prevents material loss and ensures a constant material ratio. As the polarity of the organic solvent increases, the resulting perovskite catalyst has fewer defects.

[0034] Step 4: ball mill the precursor suspension at a speed of 500 to 1000 rpm for 2 to 5 hours.

[0035] Step 5: Place the obtained sample at 60 to 100 o C oven for 24 h. The dried samples were ground for 30 min and stored in labeled sample tubes.

[0036] Step 6: Place the ground sample in a muffle furnace and calcine at a temperature of 200 to 500 o C, and keep warm for 2 to 5 hours. Finally, cool to room temperature and grind for later use. This yields a perovskite catalyst with adjustable vacancy defect density.

[0037] The perovskite prepared by the above preparation method is ABX3, A2B'B''X6, or A2B'''X6, where A is Cs; B is divalent Pb, Ge, Cu, Co, Zn, or Sn; B' is monovalent Na, Cu, Ag, or K; B'' is trivalent Bi, In, or Sb; B''' is tetravalent Sn or Ti; and X is Cl, Br, or I. By varying the polarity of the solvent, the dissolution rate of the precursor halide salt is adjusted, thereby altering the perovskite crystal growth process, thereby preparing a perovskite catalyst with adjustable vacancy defect density.

[0038] During the preparation process, the polarity of the solvent is used to assist the dissolution and recrystallization of the precursor halide salt. The vacancy defects formed will affect the capture of photogenerated charges and the adsorption capacity of the reaction molecules on the surface. Due to the difference in polarity of the solvent used, the morphology of the prepared perovskite gradually changes from a regular cube to an irregular morphology, and the grain size increases with the increase of solvent polarity.

[0039] The present invention utilizes different metal halides, such as cesium bromide (CsBr) and lead bromide (PbBr2), cesium chloride (CsCl), sodium chloride (NaCl) and bismuth chloride (BiCl3), as well as a certain amount of organic solvent, as precursor materials in the reaction system, and obtains a perovskite catalyst with adjustable vacancy defect density by ball milling for a certain period of time. Specifically, according to the stoichiometric ratio of ABX3, A2B'B''X6 or A2B'''X6 perovskite, a halide containing A is weighed, and a metal compound that can provide B, B'B'' and B''' sources and a certain amount of organic solvent are placed in a ball mill to obtain ABX3, A2B'B''X6 or A2B'''X6 perovskite, and ball milling is performed. By changing the polarity of the solvent, the dissolution speed of the precursor halide salt is adjusted, thereby changing the perovskite crystal growth process.

[0040] The present invention adopts a wet ball milling method to obtain a perovskite catalyst with adjustable vacancy defect density and a preparation method thereof. The method is simple in process, has low equipment requirements, and is highly operable. By utilizing different metal halides, such as cesium bromide (CsBr) and lead bromide (PbBr2), cesium chloride (CsCl), sodium chloride (NaCl) and bismuth chloride (BiCl3), and a certain amount of organic solvent as precursor materials, a perovskite catalyst with adjustable vacancy defect density is obtained by ball milling for a certain period of time. During the wet ball milling process, the solvent dissolves reactants such as cesium salt and halide salt. The more fully dissolved, the easier it is for the perovskite to crystallize and grow, resulting in better crystallinity of the obtained perovskite powder and more regular particle morphology, accompanied by a gradual decrease in the density of surface vacancy defects.

[0041] The perovskite catalyst with adjustable vacancy defect density prepared using the present invention can improve the catalyst's charge carrier separation ability, thereby achieving high photoelectron utilization. Furthermore, the perovskite catalyst with adjustable vacancy defect density prepared using the present invention can also achieve adjustable grain size, resulting in high photocatalytic CO2 reduction efficiency. Therefore, this preparation method promotes research on defect control technology for perovskite materials and the application of related perovskite materials in energy conversion using solar energy (including water decomposition to produce hydrogen and CO2 reduction).

[0042] Example 1

[0043] Step 1: According to the chemical composition of ABX3, 0.734g of lead bromide (PbBr2) and 0.425g of cesium bromide (CsBr) were weighed and placed in a ball mill.

[0044] Step 2: Use acetonitrile as the organic solvent, add 5 ml into the ball mill, maintain the speed at 500 rpm, and ball mill for 3 hours.

[0045] Step 3: Place the obtained sample at 100 o C oven for 24 h. The dried samples were ground for 30 min and stored in labeled sample tubes.

[0046] Step 4: Place the ground sample in a muffle furnace and calcine at a temperature of 400 o C, keep warm for 4 hours. Finally, cool to room temperature and grind for later use.

[0047] Example 2

[0048] Step 1: According to the chemical composition of ABX3, 0.734g of lead bromide (PbBr2) and 0.425g of cesium bromide (CsBr) were weighed and placed in a ball mill.

[0049] Step 2: Use organic solvent ethanol as the solvent, add 5 ml into the ball mill, maintain the speed at 500 rpm, and ball mill for 3 hours.

[0050] Step 3: Place the obtained sample at 100 o C oven for 24 h. The dried samples were ground for 30 min and stored in labeled sample tubes.

[0051] Step 4: Place the ground sample in a muffle furnace and calcine at a temperature of 400 o C, keep warm for 4 hours. Finally, cool to room temperature and grind for later use.

[0052] Example 3

[0053] Step 1: According to the chemical composition of ABX3, 0.734g of lead bromide (PbBr2) and 0.425g of cesium bromide (CsBr) were weighed and placed in a ball mill.

[0054] Step 2: Select organic solvent carbon tetrachloride as the solvent, add 5 ml into the ball mill, maintain the speed at 500 rpm, and ball mill for 3 hours.

[0055] Step 3: Place the obtained sample at 100 o C oven for 24 h. The dried samples were ground for 30 min and stored in labeled sample tubes.

[0056] Step 4: Place the ground sample in a muffle furnace and calcine at a temperature of 400 o C, keep warm for 4 hours. Finally, cool to room temperature and grind for later use.

[0057] Example 4

[0058] Step 1: According to the chemical composition of ABX3, 0.734g of lead bromide (PbBr2) and 0.425g of cesium bromide (CsBr) were weighed and placed in a ball mill.

[0059] Step 2: Use organic solvent hexane as solvent, add 5 ml into the ball mill, maintain the speed at 500 rpm, and ball mill for 3 hours.

[0060] Step 3: Place the obtained sample at 100 o C oven for 24 h. The dried samples were ground for 30 min and stored in labeled sample tubes.

[0061] Step 4: Place the ground sample in a muffle furnace and calcine at a temperature of 400 o C, keep warm for 4 hours. Finally, cool to room temperature and grind for later use.

[0062] The microstructure of the samples finally prepared in Example 1 to Example 4 was observed. Figure 2As shown in Figure 2, the morphology of the prepared perovskite gradually changes from regular cubic to irregular as the solvent polarity is adjusted (acetonitrile > ethanol > carbon tetrachloride > hexane). Meanwhile, the grain size increases with increasing solvent polarity. This is because during the wet ball milling process, as the solvent polarity decreases, the dissolution and recrystallization rates of CsBr and PbBr2 slow, resulting in a gradual decrease in the crystallinity of the resulting CsPbBr3.

[0063] Depend on Figure 3 As shown, as the Br / Pb ratio decreases, the electron paramagnetic resonance peak intensity corresponding to the Br vacancy defect gradually increases, proving that the defect density of the perovskite catalyst with adjustable vacancy defect density prepared by the present invention is inversely proportional to the polarity of the organic solvent.

[0064] The present invention also discloses that the above-mentioned perovskite catalyst can be used for photothermal catalytic CO2 reduction, such as Figure 4 As shown, the catalyst exhibits stronger CO2 adsorption capacity and increased normalized reaction electron number with increasing Br vacancy defect density, indicating the promoting effect of Br vacancy defects on the photothermal CO2 reduction of CsPbBr3 powder.

[0065] Example 5

[0066] Step 1. According to the chemical composition of A2B'B''X6, 0.337 g of cesium chloride (CsCl), 0.585 g of sodium chloride (NaCl), and 3.153 g of bismuth chloride (BiCl3) were weighed and placed in a ball mill.

[0067] Step 2: Use organic solvent ethanol as the solvent, add 15 ml into the ball mill, maintain the speed at 500 rpm, and ball mill for 3 hours.

[0068] Step 3: Place the sample at 80 o C oven for 24 h. The dried samples were ground for 30 min and stored in labeled sample tubes.

[0069] Step 4: Place the ground sample in a muffle furnace and calcine at a temperature of 300 o C, keep warm for 5 hours, and finally cool to room temperature before grinding for later use.

[0070] Example 6

[0071] Step 1: According to the chemical composition of A2B'B''X6, 0.852 g of cesium chloride (CsBr), 0.898 g of bismuth bromide (BiBr3) and 0.188 g of silver bromide (AgBr) were weighed and placed in a ball mill.

[0072] Step 2: Use acetonitrile as the organic solvent, add 7 ml into the ball mill, maintain the speed at 500 rpm, and ball mill for 3 hours.

[0073] Step 3: Place the sample at 70 o C oven for 24 h. The dried samples were ground for 30 min and stored in labeled sample tubes.

[0074] Step 4: Place the ground sample in a muffle furnace and calcine at a temperature of 250 o C, keep warm for 5 hours, and finally cool to room temperature before grinding for later use.

[0075] Example 7

[0076] According to the chemical composition of ABX3, 0.734g of lead bromide (PbBr2) and 0.425g of cesium bromide (CsBr) were weighed and placed in a ball mill jar.

[0077] Step 2: Use organic solvent hexane as solvent, add 10 ml into the ball mill, maintain the speed at 800 rpm, and ball mill for 3 hours.

[0078] Step 3: Place the obtained sample at 100 o C oven for 24 h. The dried samples were ground for 30 min and stored in labeled sample tubes.

[0079] Step 4: Place the ground sample in a muffle furnace and calcine at a temperature of 400 o C, keep warm for 5 hours, and finally cool to room temperature before grinding for later use.

[0080] Example 8

[0081] Step 1: According to the chemical composition of A4BX6, 0.367 g of lead bromide (PbBr2) and 0.852 g of cesium bromide (CsBr) were weighed and placed in a ball mill.

[0082] Step 2: Select organic solvent pentane as the solvent, add 7 ml into the ball mill, maintain the speed at 800 rpm, and ball mill for 3 hours.

[0083] Step 3: Place the sample at 80 o C oven for 24 h. The dried samples were ground for 30 min and stored in labeled sample tubes.

[0084] Step 4: Place the ground sample in a muffle furnace and calcine at a temperature of 350 o C, keep warm for 4 hours. Finally, cool to room temperature and grind for later use.

[0085] Example 9

[0086] Step 1. According to the chemical composition of A2B'''X6, 0.425g of cesium bromide (CsBr) and 0.438g of tin bromide (SnBr4) were weighed and placed in a ball mill.

[0087] Step 2: Select organic solvent pentane as the solvent, add 7 ml into the ball mill, maintain the speed at 800 rpm, and ball mill for 3 hours.

[0088] Step 3: Place the sample at 80 o C oven for 24 h. The dried samples were ground for 30 min and stored in labeled sample tubes.

[0089] Step 4: Place the ground sample in a muffle furnace and calcine at a temperature of 350 o C, keep warm for 4 hours. Finally, cool to room temperature and grind for later use.

[0090] Example 10

[0091] Step 1. According to the chemical composition of A2B'''X6, 0.425g of cesium bromide (CsBr) and 0.438g of tin bromide (SnBr4) were weighed and placed in a ball mill.

[0092] Step 2: Use organic solvent ethanol as the solvent, add 5 ml into the ball mill, maintain the speed at 1000 rpm, and ball mill for 3 hours.

[0093] Step 3: Place the sample at 80 o C oven for 24 h. The dried samples were ground for 30 min and stored in labeled sample tubes.

[0094] Step 4: Place the ground sample in a muffle furnace and calcine at a temperature of 200 o C, keep warm for 5 hours, and finally cool to room temperature before grinding for later use.

[0095] Example 11

[0096] Step 1: According to the chemical composition of ABX3, 0.88g of copper chloride and 1.11g of cesium chloride were weighed and placed in a ball mill.

[0097] Step 2: Use organic solvent hexane as solvent, add 10 ml into the ball mill, maintain the speed at 1000 rpm, and ball mill for 2 hours.

[0098] Step 3: Place the sample at 60 o C oven for 24 h. The dried samples were ground for 30 min and stored in labeled sample tubes.

[0099] Step 4: Place the ground sample in a muffle furnace and calcine at a temperature of 500 oC, keep warm for 2 hours. Finally, cool to room temperature and grind for later use.

Claims

1. A method for preparing a perovskite catalyst with adjustable vacancy defect density, characterized in that: The following steps are involved: Step 1: mixing perovskite precursor powder and an organic reagent to obtain a perovskite precursor suspension; The perovskite precursor powder is prepared by mixing a halide of A and a metal compound; the metal compound is a metal compound of B, a metal compound of B', a metal compound of B'', or a metal compound of B'''; the anions in the halide of A and the metal compound are the same; the organic reagent is a non-polar reagent, a medium-level reagent, or a strong polar reagent; Step 2, ball milling the perovskite precursor suspension to obtain a ball milled sample; Step 3: drying the ball-milled sample and then calcining it to obtain a perovskite catalyst with adjustable vacancy defect density; as the polarity of the organic reagent increases, the defect density of the perovskite catalyst decreases; Among them, the calcination temperature is 200 ~ 500 o C, calcination time is 2 to 5 hours; The perovskite catalyst is ABX3, A2B'B''X6 or A2B'''X6, wherein A is Cs; B is divalent Pb, Ge, Cu, Co, Zn or Sn; B' is monovalent Na, Cu, Ag or K; B'' is trivalent Bi, In or Sb; B''' is tetravalent Sn or Ti; and X is Cl, Br or I.

2. The method for preparing a perovskite catalyst with adjustable vacancy defect density according to claim 1, wherein: In step 1, the halide of A is cesium chloride, cesium bromide or cesium iodide.

3. The method for preparing a perovskite catalyst with adjustable vacancy defect density according to claim 1, wherein: In step 1, the metal compound of B is lead chloride, lead bromide, zinc bromide, copper bromide, cobalt bromide, lead iodide or lead acetate; the metal compound of B' is sodium chloride, potassium chloride, copper chloride, silver chloride, sodium bromide, potassium bromide, copper bromide, silver bromide, sodium iodide, potassium iodide, copper iodide or silver iodide; the metal compound of B'' is bismuth trichloride, indium trichloride, antimony trichloride, bismuth tribromide, indium tribromide, antimony tribromide, bismuth triiodide, indium triiodide, antimony triiodide; the metal compound of B''' is tin tetrachloride, tin tetrabromide, tin tetraiodide and titanium tetrachloride, titanium tetrabromide or titanium tetraiodide.

4. The method for preparing a perovskite catalyst with adjustable vacancy defect density according to claim 1, wherein: The non-polar reagent is cyclohexane, petroleum ether, hexane or pentane; the intermediate polar reagent is carbon tetrachloride, ethyl acetate, chloroform, dichloromethane, ether or toluene; and the strong polar reagent is acetic acid, acetonitrile, methanol, ethanol or isopropanol.

5. The method for preparing a perovskite catalyst with adjustable vacancy defect density according to claim 1, wherein: In step 2, the ball milling speed is 500 to 1000 rpm, and the ball milling time is 2 to 5 h.

6. The method for preparing a perovskite catalyst with adjustable vacancy defect density according to claim 1, characterized in that: In step 3, the drying temperature is 60 ~ 100 o C, drying time is 24 h.

7. The method for preparing a perovskite catalyst with adjustable vacancy defect density according to claim 1, characterized in that: In step 1, after adding the halide of A and the metal compound into the ball mill, an organic solvent is added into the ball mill.

8. A perovskite catalyst with adjustable vacancy defect density obtained by the preparation method according to any one of claims 1 to 7, characterized in that: The perovskite catalyst is ABX3, A2B'B''X6 or A2B'''X6, wherein A is Cs; B is divalent Pb, Ge, Cu, Co, Zn or Sn; B' is monovalent Na, Cu, Ag or K; B'' is trivalent Bi, In or Sb; B''' is tetravalent Sn or Ti; and X is Cl, Br or I.

9. Use of the perovskite catalyst with adjustable vacancy defect density according to claim 8, characterized in that: Used for photothermal catalytic CO2 reduction or water decomposition to produce hydrogen.

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