Defect-state semiconductor / ZnCuInS x Se 1-x Preparation of composite catalysts and their application in photocatalysis

Abstract

The application discloses a kind of defect state semiconductor / ZnCuInS x Se 1‑x Preparation of composite catalyst and application in photocatalysis, defect state semiconductor is carrier, and ZnCuInS x Se 1‑x Quantum dot preparation composite catalyst, wherein 0 < x < 1.Defect state semiconductor and ZnCuInS x Se 1‑x Quantum dot is uniformly dispersed in water respectively by ultrasonic, then the two are mixed and stirred to be uniform, the obtained precipitate is washed by centrifugation, and the composite catalyst is obtained after drying.The preparation method of the application is simple and feasible, convenient to operate, and ZCISSe can be uniformly loaded on the surface of defect state semiconductor, and has relatively close contact with semiconductor.The prepared defect state semiconductor / ZCISSe composite catalyst can be used in the fields of photocatalytic reduction of carbon dioxide, photolysis of water and photodegradation, and is preferentially selected for photocatalytic reduction of carbon dioxide reaction.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis, and particularly relates to a defect-state semiconductor / ZnCuInS x Se 1-x Preparation of composite catalysts and their application in photocatalysis. Background Technology

[0002] With the rapid development of human society, energy shortages and environmental pollution have become increasingly serious problems. Semiconductor photocatalysis technology, with its advantages of low pollution, mild reaction conditions, and low energy consumption, has become a research hotspot in the international academic community. In recent years, utilizing photocatalysis technology to degrade pollutants and convert CO2 into high-value-added chemicals holds promise for simultaneously solving the problems of carbon emissions and energy shortages, and is of significant research importance for my country's "dual-carbon" strategic goals. However, current photocatalysis technology still faces the challenge of low catalytic efficiency, and the development of highly efficient photocatalysts is the core of catalytic technology.

[0003] Highly efficient semiconductor photocatalysts must simultaneously meet two conditions: firstly, they need a relatively narrow band gap for strong light absorption in the visible light region; secondly, they need a large band gap to facilitate the thermodynamics of the photocatalytic reaction. Therefore, the expected requirements for photocatalysts in terms of light capture and photocatalytic reaction thermodynamics are contradictory. Furthermore, for single-component photocatalysts, the generation, separation, and surface redox reactions of photogenerated carriers occur simultaneously on a single semiconductor, leading to severe recombination of photogenerated electrons and holes. The construction of Z-type heterojunctions can not only resolve the contradiction between light capture and photocatalytic thermodynamics but also achieve effective spatial separation of photogenerated electrons and holes while maintaining their stronger redox capabilities at different active sites, making it a highly effective strategy for constructing highly active photocatalytic systems.

[0004] Metal sulfide quantum dots ZnCuInS x Se 1-x ZCISSe exhibits excellent visible light absorption and strong photogenerated electron reduction capabilities, showing great potential in the field of photocatalysis. However, ZCISSe quantum dots are prone to aggregation, leading to a reduction in their catalytic active sites; simultaneously, severe recombination of photogenerated electrons and holes in a single ZCISSe dot gradually decreases its photoreduction activity. These issues severely restrict the application of ZCISSe in photocatalysis.

[0005] Although there are patent reports on carbon nitride / quantum dot related work (CN201611102093, CN201811147810, CN201910122111, CN202010938845, CN202011626170), the quantum dots loaded with carbon nitride in the above patents are still prone to agglomeration because carbon nitride lacks anchoring centers. Summary of the Invention

[0006] To address the problems in existing technologies and to overcome the drawbacks of ZCISSe quantum dots' easy aggregation and severe recombination of photogenerated electrons and holes, this invention introduces two-dimensional defect-state nanosheets as a support to prepare composite catalysts, providing a new research approach to solve these problems. On one hand, the defect-state semiconductor can anchor ZCISSe quantum dots, reducing ZCISSe aggregation and thus increasing the exposed catalytic active sites. On the other hand, the construction of a heterojunction between the two inhibits the recombination of photogenerated electrons and holes, improving their separation efficiency.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A defect-state semiconductor / ZnCuInS x Se 1-x The method for preparing composite catalysts uses defect-state semiconductors as supports, and directly anchors ZnCuInS based on defects on the semiconductor surface. x Se 1-x Quantum dot preparation of composite catalysts, wherein 0 <x<1。

[0009] Furthermore, the defect-state semiconductor / ZnCuInS x Se 1-x The preparation method of the composite catalyst includes the following steps: at room temperature, defect-state semiconductors are ultrasonically dispersed in water, and then ZnCuInS is added. x Se 1-x Quantum dots are ultrasonically stirred until homogeneous, the precipitate is washed by centrifugation, and then dried to obtain a composite catalyst.

[0010] Furthermore, the defective semiconductor includes defective carbon nitride (C3N4) nanosheets, defective bismuth tungstate (Bi2WO6) nanosheets, and defective bismuth molybdate (Bi2MoO6) nanosheets, with C3N4 being the preferred choice.

[0011] Furthermore, the defect-state semiconductor and ZnCuInS x Se 1-x The mass ratio of quantum dots is 20:(1-7).

[0012] Furthermore, the preparation method of defective carbon nitride (C3N4) nanosheets is as follows: 0.005-0.015g NaOH is dissolved in 40mL H2O, then 10g urea is added and stirred until dissolved. The mixture is then dried in an oven at 80℃ overnight. After drying, the sample is ground in a mortar and pestle. The resulting sample is placed in a crucible and subjected to a first heat treatment at 550℃ for 1-4h, preferably 2h. After cooling and grinding, the sample is placed in a porcelain boat and subjected to a second heat treatment at 500℃ for 1-4h, preferably 2h. After cooling and grinding, defective C3N4 nanosheets are obtained.

[0013] Furthermore, the preparation method of defective bismuth tungstate (Bi2WO6) nanosheets is as follows: 3.75 mmol Bi(NO)3·5H2O and 1.875 mmol Na2WO4·2H2O were dissolved in 30 mL of ethylene glycol and reacted in an oven at 160 °C for 12 h. The resulting powder was centrifuged, washed, dried overnight, ground, and placed in a porcelain boat, then calcined in a muffle furnace at 400 °C for 4 h. 0.1 g Bi2WO6 was ultrasonically dispersed in 25 mL of H2SO4 solution (0.5-3 mol / L), transferred to a high-pressure reactor, and reacted at 100 °C for 12 h. After washing several times with deionized water and anhydrous ethanol, it was dried in an oven at 60 °C overnight to obtain defective Bi2WO6.

[0014] Furthermore, the preparation method of defective bismuth molybdate (Bi₂MoO₆) nanosheets is as follows: 3.75 mmol Bi(NO)₃·5H₂O and 1.875 mmol Na₂MoO₄·2H₂O were dissolved in 30 mL of ethylene glycol and reacted in an oven at 160 °C for 12 h. The resulting powder was centrifuged, washed, dried overnight, ground, and placed in a porcelain boat, then calcined in a muffle furnace at 400 °C for 4 h. 0.1 g Bi₂MoO₆ was ultrasonically dispersed in 25 mL of H₂SO₄ solution (0.5–3 mol / L), transferred to a high-pressure reactor, and reacted at 100 °C for 12 h. After washing several times with deionized water and anhydrous ethanol, it was dried in an oven at 60 °C overnight to obtain defective Bi₂MoO₆.

[0015] Furthermore, ZnCuInS was synthesized using a high-temperature hot-injection method. x Se 1-x Quantum dots were first prepared by dissolving 0.0128 g of sulfur powder and 0.0479 g of selenium powder in diphenylphosphine to form an anionic precursor solution. Then, 0.2 mmol of indium acetate, 0.14 mmol of CuI, and 0.08 mmol of zinc acetate were dissolved in oleylamine solution to obtain mixture A. Mixture A was then injected into the anionic precursor solution at 170 °C, and the reaction was carried out at 220 °C for 5 min. After the reaction, the resulting mixture was dispersed in n-hexane and transferred to a centrifuge tube. Anhydrous ethanol was added, and the mixture was centrifuged and purified. Finally, it was dispersed in CH2Cl2 solution.

[0016] Furthermore, the defect-state semiconductor / ZnCuInS of the present invention x Se 1-x A typical preparation method for composite catalysts is as follows: Weigh 3 mg of ZnCuInS x Se 1-x Quantum dots were added to 30 mL of water and sonicated until they were completely dissolved. 20 mg of defective C3N4 nanosheets were sonicated and uniformly dispersed in 20 mL of aqueous solution. The two were then mixed and stirred until homogeneous, and centrifuged and dried to obtain the composite catalyst, denoted as CN-X / ZCISSe (X is the mass of NaOH in the preparation of defective C3N4 nanosheets).

[0017] This invention also provides a defect-state semiconductor / ZnCuInS prepared using the aforementioned method. x Se 1-x The application of composite catalysts in photocatalysis, wherein the photocatalysis includes photocatalytic reduction of carbon dioxide, photocatalytic water splitting, and photodegradation; the photocatalytic reduction of carbon dioxide reaction is preferred.

[0018] The beneficial effects of this invention are as follows: This invention prepares a composite catalyst by anchoring ZCISSe quantum dots to a defect-state semiconductor. The construction of the heterojunction between the two suppresses the recombination of photogenerated electrons and holes, improving the separation efficiency of photogenerated carriers. Furthermore, the defect-state semiconductor can anchor ZCISSe quantum dots, reducing ZCISSe aggregation and increasing the exposed catalytic active sites. The preparation method of this invention is simple, feasible, and convenient to operate. ZCISSe can be uniformly loaded on the surface of the defect-state semiconductor, and there is a relatively close contact between the ZCISSe and the semiconductor. The obtained defect-state semiconductor / ZCISSe composite catalyst can be used in photocatalytic reduction of carbon dioxide, photocatalytic water splitting, and photodegradation, with photocatalytic reduction of carbon dioxide being the preferred reaction. Attached Figure Description

[0019] Figure 1 The image shows the XRD pattern of the catalyst prepared in Example 2.

[0020] Figure 2 The images are TEM images of the catalysts prepared in Example 2 and Comparative Example 1, (ab) CN-0.01 / ZCISSe, (c) CN / ZCISSe.

[0021] Figure 3 Graphs showing the yield of CO, a product of photocatalytic reduction, of the catalysts prepared in Examples 1 and 2, and Comparative Examples 1 and 4.

[0022] Figure 4 The diagram shows the photocatalytic degradation of tetracycline hydrochloride by the catalysts prepared in Examples 1 and 2 and Comparative Example 1.

[0023] Figure 5 The graph shows the yield of CO, a product of photocatalytic reduction, of the catalysts prepared in Examples 2 and Comparative Examples 2-3. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make some non-essential improvements and adjustments based on the above-described invention.

[0025] Example 1

[0026] The preparation method of the defective CN-0.005 / ZCISSe composite catalyst in this embodiment is as follows:

[0027] (1) Preparation of defective CN-0.005 nanosheets

[0028] Two-dimensional C3N4 nanosheets were prepared from urea through a secondary calcination process. 10g of urea was weighed and placed in a crucible, then heat-treated at 550℃ for 2 hours. After cooling and grinding, the nanosheets were placed in a porcelain boat and heat-treated again at 500℃ for 2 hours. After cooling and grinding, the two-dimensional C3N4 nanosheets were obtained.

[0029] Two-dimensional defective C3N4 nanosheets were prepared by alkalization treatment. Specifically, 0.005 g of NaOH was dissolved in 40 mL of H2O, and then 10 g of urea was added and stirred until dissolved. The solution was dried in an oven at 80 °C overnight, and then ground in a mortar. The resulting sample was placed in a crucible and heat-treated at 550 °C for 2 hours. After cooling and grinding, the sample was placed in a porcelain boat and heat-treated again at 500 °C for 2 hours. After cooling and grinding, defective C3N4 nanosheets were obtained, denoted as CN-0.005 (where 0.005 represents the mass of NaOH used in the preparation of the defective C3N4 nanosheets).

[0030] (2) Preparation of ZCISSe quantum dots: ZnCuInS was synthesized by high-temperature hot-injection method. x Se 1-x Quantum dots were first prepared by dissolving 0.0128 g of sulfur powder and 0.0479 g of selenium powder in diphenylphosphine to form an anionic precursor solution. Then, 0.2 mmol of indium acetate, 0.14 mmol of CuI, and 0.08 mmol of zinc acetate were dissolved in oleylamine solution to obtain mixture A. Mixture A was then injected into the anionic precursor solution at 170 °C, and the reaction was carried out at 220 °C for 5 min. After the reaction, the resulting mixture was dispersed in n-hexane and transferred to a centrifuge tube. Anhydrous ethanol was added, and the mixture was centrifuged and purified. Finally, it was dispersed in CH2Cl2 solution.

[0031] (3) Preparation of defect-state CN-0.005 / ZCISSe composite catalyst: At room temperature, 3 mg of ZnCuInS was weighed. x Se 1-x Add quantum dots to 30 mL of water and sonicate until the quantum dots are completely dissolved; add 20 mg CN-0.005 (or sonicate 20 mg of defective CN-0.005 nanosheets uniformly dispersed in 20 mL of aqueous solution), sonicate and stir until uniformly mixed, centrifuge and dry to obtain the composite catalyst, denoted as CN-0.005 / ZCISSe.

[0032] Example 2

[0033] The preparation method of the defective CN-0.01 / ZCISSe composite catalyst in this embodiment is as follows:

[0034] (1) Preparation of defective CN-0.01 nanosheets

[0035] Two-dimensional C3N4 nanosheets were prepared from urea through a secondary calcination process. 10g of urea was weighed and placed in a crucible, then heat-treated at 550℃ for 2 hours. After cooling and grinding, the nanosheets were placed in a porcelain boat and heat-treated again at 500℃ for 2 hours. After cooling and grinding, the two-dimensional C3N4 nanosheets were obtained.

[0036] Two-dimensional defective C3N4 nanosheets were prepared by an alkalization treatment method. Specifically, 0.01 g of NaOH was dissolved in 40 mL of H2O, and then 10 g of urea was added and stirred until dissolved. The solution was dried in an oven at 80 °C overnight, and then ground in a mortar. The resulting sample was placed in a crucible and heat-treated at 550 °C for 2 hours. After cooling and grinding, the sample was placed in a porcelain boat and heat-treated again at 500 °C for 2 hours. After cooling and grinding, defective C3N4 nanosheets, denoted as CN-0.01, were obtained.

[0037] (2) The preparation method of ZCISSe quantum dots is the same as in Example 1.

[0038] (3) Preparation of defect-state CN-0.01 / ZCISSe composite catalyst: At room temperature, 3 mg of ZnCuInS x Se 1-x Quantum dots were added to 30 mL of water and sonicated until they were completely dissolved. 20 mg of defective CN-0.01 nanosheets were sonicated and uniformly dispersed in 20 mL of aqueous solution. The two were then mixed and stirred until homogeneous, and centrifuged and dried to obtain the composite catalyst, denoted as CN-0.01 / ZCISSe.

[0039] Example 3

[0040] The preparation method of the defective Bi2WO6 / ZCISSe composite catalyst in this embodiment is as follows:

[0041] (1) Preparation of defective Bi2WO6 nanosheets

[0042] 3.75 mmol Bi(NO)3·5H2O and 1.875 mmol Na2WO4·2H2O were dissolved in 30 mL of ethylene glycol and reacted in an oven at 160 °C for 12 h. The resulting powder was centrifuged, washed, dried overnight, ground, and placed in a porcelain boat, then calcined in a muffle furnace at 400 °C for 4 h. 0.1 g Bi2WO6 was ultrasonically dispersed in 25 mL of H2SO4 solution (0.5-3 mol / L), transferred to a high-pressure reactor, and reacted at 100 °C for 12 h. After washing several times with deionized water and anhydrous ethanol, it was dried in an oven at 60 °C overnight to obtain defective Bi2WO6.

[0043] (2) The preparation method of ZCISSe quantum dots is the same as in Example 1.

[0044] (3) Preparation of defective Bi2WO6 / ZCISSe composite catalyst: Weigh 1 mg of ZCISSe quantum dots and add 30 mL of water, sonicate until the quantum dots are completely dissolved. Add 20 mg of defective Bi2WO6 nanosheets obtained in step (1), sonicate and stir until the two are uniformly mixed, and centrifuge and dry to obtain the composite catalyst.

[0045] Example 4

[0046] The preparation method of the defective Bi2MoO6 / ZCISSe composite catalyst in this embodiment is as follows:

[0047] (1) Preparation of defective Bi2MoO6 nanosheets

[0048] 3.75 mmol Bi(NO)3·5H2O and 1.875 mmol Na2MoO4·2H2O were dissolved in 30 mL of ethylene glycol and reacted in an oven at 160 °C for 12 h. The resulting powder was centrifuged, washed, dried overnight, ground, and placed in a porcelain boat, then calcined in a muffle furnace at 400 °C for 4 h. 0.1 g Bi2MoO6 was ultrasonically dispersed in 25 mL of H2SO4 solution (0.5-3 mol / L), transferred to a high-pressure reactor, and reacted at 100 °C for 12 h. After washing several times with deionized water and anhydrous ethanol, it was dried in an oven at 60 °C overnight to obtain defective Bi2MoO6.

[0049] (2) The preparation method of ZCISSe quantum dots is the same as in Example 1.

[0050] (3) Preparation of defective Bi2WO6 / ZCISSe composite catalyst: Weigh 7 mg of ZCISSe quantum dots and add 30 mL of water, sonicate until the quantum dots are completely dissolved. Add 20 mg of defective Bi2MoO6 nanosheets obtained in step (1), sonicate and stir until the two are uniformly mixed, and centrifuge and dry to obtain the composite catalyst.

[0051] Comparative Example 1

[0052] Based on Example 1, defective C3N4 nanosheets, i.e. CN-0.01, were replaced with defect-free C3N4 nanosheets. The remaining steps were the same as in Example 1, and the resulting catalyst was denoted as CN / ZCISSe.

[0053] Figure 1 The XRD patterns of the defective C3N4 / ZCISSe composite catalysts prepared in Examples 1 and 2 are shown. The results show that the prepared composite catalysts are free of impurities and are relatively pure.

[0054] Figure 2 The images show TEM images of the catalysts prepared in Example 1 and Comparative Example 1. The results show that ZCISSe quantum dots are uniformly loaded onto two-dimensional defect-state C3N4 nanosheets. Compared to defective ones, quantum dots loaded on defect-free C3N4 nanosheets are more prone to aggregation.

[0055] Comparative Example 2

[0056] Based on Example 1, ZCISSe quantum dots were replaced with ZCIS quantum dots, and the remaining steps were the same as in Example 1, to obtain C3N4 nanosheets loaded with pure S quantum dots, denoted as CN-0.01 / ZCIS. The preparation method of ZCIS quantum dots is as follows: First, 0.065g of S powder was dissolved in diphenylphosphine to form an anionic precursor solution. 0.2mmol of indium acetate, 0.14mmol of CuI and 0.08mmol of zinc acetate were dissolved in oleylamine solution to obtain mixture A. Mixture A was injected into the anionic precursor solution at 170℃, and then reacted at 220℃ for 5min. After the reaction, the resulting mixture was dispersed in n-hexane and then transferred to a centrifuge tube. Anhydrous ethanol was added and centrifuged for purification, and then dispersed in CH2Cl2 solution.

[0057] Comparative Example 3

[0058] Based on Example 1, ZCISSe quantum dots were replaced with ZCISe quantum dots, and the remaining steps were the same as in Example 1, to obtain C3N4 nanosheets loaded with pure Se quantum dots, denoted as CN-0.01 / ZCISe. The preparation method of ZCISe quantum dots is as follows: First, 0.158g of Se powder was dissolved in diphenylphosphine to form an anionic precursor solution. 0.2mmol of indium acetate, 0.14mmol of CuI and 0.08mmol of zinc acetate were dissolved in oleylamine solution to obtain mixture A. Mixture A was injected into the anionic precursor solution at 170℃, and then reacted at 220℃ for 5min. After the reaction, the resulting mixture was dispersed in n-hexane and then transferred to a centrifuge tube. Anhydrous ethanol was added and centrifuged for purification, and then dispersed in CH2Cl2 solution.

[0059] Comparative Example 4

[0060] The preparation method of the defective CN-0.02 / ZCISSe composite catalyst is as follows:

[0061] (1) Preparation of defective C3N4 nanosheets

[0062] Two-dimensional C3N4 nanosheets were prepared from urea through a secondary calcination process. 10g of urea was weighed and placed in a crucible, then heat-treated at 550℃ for 2 hours. After cooling and grinding, the nanosheets were placed in a porcelain boat and heat-treated again at 500℃ for 2 hours. After cooling and grinding, the two-dimensional C3N4 nanosheets were obtained.

[0063] Two-dimensional defective C3N4 nanosheets were prepared by an alkalization treatment method. Specifically, 0.02 g of NaOH was dissolved in 40 mL of H2O, and then 10 g of urea was added and stirred until dissolved. The solution was dried in an oven at 80 °C overnight, and then ground in a mortar. The resulting sample was placed in a crucible and heat-treated at 550 °C for 2 hours. After cooling and grinding, the sample was placed in a porcelain boat and heat-treated again at 500 °C for 2 hours. After cooling and grinding, defective C3N4 nanosheets, denoted as CN-0.02, were obtained.

[0064] (2) The preparation method of ZCISSe quantum dots is the same as in Example 1.

[0065] (3) Preparation of defective CN-0.02 / ZCISSe composite catalyst: At room temperature, weigh 3 mg of ZCISSe quantum dots and add them to 30 mL of water, and sonicate until the quantum dots are completely dissolved; sonicate 20 mg of defective CN-0.02 nanosheets and disperse them uniformly in 20 mL of aqueous solution; then mix and stir the two together until uniform, and centrifuge and dry to obtain the composite catalyst, denoted as CN-0.02 / ZCISSe.

[0066] 1. Photocatalytic carbon dioxide reduction reaction

[0067] Prepare 50 mL of aqueous solution, weigh 30 mg of the catalyst obtained in Examples 1-2 and Comparative Examples 1-4 above, and add it to the solution. Sonicate for half an hour to ensure the catalyst is uniformly dispersed in the solution. First, evacuate the reaction system under darkness for half an hour to remove air from the system. Then, under xenon lamp irradiation, analyze the reduction products using gas chromatography every 0.5 h. The results are as follows. Figure 3-5 As shown.

[0068] 2. Catalytic degradation of tetracycline hydrochloride

[0069] Prepare 50 mL of tetracycline hydrochloride solution (concentration 100 mg / L), weigh 25 mg of the catalyst obtained in Examples 1 and 2 above and add it to the solution. Sonicate for half an hour to ensure the catalyst is uniformly dispersed in the solution. Stir for 30 min in the dark and take a sample as a blank sample. Then, under xenon lamp irradiation, take samples every 10 min. Finally, measure the light absorption of tetracycline hydrochloride using a UV-Vis spectrophotometer and plot the absorbance versus time curve. The photocatalytic test results are shown in [Figure number missing]. Figure 3-5 .

[0070] from Figure 3 and 4 As can be seen, the construction of the defect-state CN / ZCISSe composite catalytic system effectively separates photogenerated electrons and holes. Compared with C3N4 alone, the efficiency of photocatalytic degradation of tetracycline hydrochloride and the amount of carbon monoxide produced by photocatalytic reduction of carbon dioxide are significantly improved. Furthermore, with increasing NaOH content, the photocatalytic activity of the composite catalyst first increases and then decreases, reaching its highest level when the NaOH content is 0.01 g.

[0071] from Figure 5 The results show that the catalytic efficiency of C3N4 nanosheets supported by ZCISSe quantum dots is significantly higher than that of C3N4 nanosheets supported by pure S and pure Se quantum dots.

[0072] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A defect-state semiconductor / ZnCuInS x Se 1-x A method for preparing a composite catalyst, characterized in that: Using defect-state semiconductors as carriers, ZnCuInS is directly anchored using defects on the semiconductor surface. x Se 1-x Quantum dot preparation of composite catalysts, wherein 0 <x<1; The defect-state semiconductor / ZnCuInS x Se 1-x The preparation method of the composite catalyst includes the following steps: at room temperature, defect-state semiconductors are ultrasonically dispersed in water, and then ZnCuInS is added. x Se 1-x Quantum dots were ultrasonically stirred until homogeneous, and the resulting precipitate was washed by centrifugation and dried to obtain a composite catalyst. The defect-state semiconductor is a defect-state C3N4 nanosheet; The preparation method of defective C3N4 nanosheets is as follows: 0.005-0.015g NaOH is dissolved in 40 mL H2O, then 10g urea is added and stirred until dissolved. The mixture is dried in an oven at 80℃ overnight. After drying, it is crushed in a mortar. The resulting sample is placed in a crucible and subjected to a first heat treatment at 550℃ for 1-4 h. After cooling and grinding, it is placed in a porcelain boat and subjected to a second heat treatment at 500℃ for 1-4 h. After cooling and grinding, defective C3N4 nanosheets can be obtained. ZnCuInS was synthesized using a high-temperature hot-injection method. x Se 1-x Quantum dots were first prepared by dissolving 0.0128 g S powder and 0.0479 g Se powder in diphenylphosphine to form an anionic precursor solution. 0.2 mmol indium acetate, 0.14 mmol CuI, and 0.08 mmol zinc acetate were dissolved in oleylamine solution to obtain mixture A. Mixture A was injected into the anionic precursor solution at 170 °C, and the reaction was carried out at 220 °C for 5 min. After the reaction, the resulting mixture was dispersed in n-hexane and transferred to a centrifuge tube. Anhydrous ethanol was added, and the mixture was centrifuged and purified. Finally, it was dispersed in CH2Cl2 solution.

2. The defect-state semiconductor / ZnCuInS according to claim 1 x Se 1-x A method for preparing a composite catalyst, characterized in that: The defect-state semiconductor and ZnCuInS x Se 1-x The mass ratio of quantum dots is 20:(1-7).

3. The defect-state semiconductor / ZnCuInS according to claim 1 x Se 1-x A method for preparing a composite catalyst, characterized in that: Weigh out 3 mg of ZnCuInS at room temperature. x Se 1-x Quantum dots were added to 30 mL of water and sonicated until they were completely dissolved. 20 mg of defective C3N4 nanosheets were sonicated and uniformly dispersed in 20 mL of aqueous solution. The two were then mixed and stirred until homogeneous, and centrifuged and dried to obtain the composite catalyst.

4. The defect-state semiconductor / ZnCuInS prepared by the method according to any one of claims 1-3 x Se 1-x The application of composite catalysts in photocatalysis is characterized by: The photocatalysis includes photocatalytic reduction of carbon dioxide, photocatalytic water splitting, and photocatalytic degradation of tetracycline hydrochloride.

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