Catalyst of titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres with zinc and oxygen double vacancies, preparation method and application

Abstract

The application discloses a kind of hollow microspheres of titanium dioxide / cadmium zinc sulfide heterojunction with zinc, oxygen double vacancies, the preparation method of the catalyst of the hollow microspheres of titanium dioxide / cadmium zinc sulfide heterojunction and the catalyst application of the hollow microspheres of titanium dioxide / cadmium zinc sulfide heterojunction.The hollow microspheres of titanium dioxide / cadmium zinc sulfide heterojunction with zinc, oxygen double vacancies of the application, the preparation method of the catalyst of the heterojunction hollow microspheres and the preparation method of the application of the double vacancies heterojunction hollow microspheres are in situ preparation method using one-step hydrothermal method, and double vacancies heterojunction is constructed on the surface of titanium dioxide hollow microspheres, which has the advantages of high activity stability, simple preparation process and controllable reaction conditions.The heterojunction hollow microspheres have wide visible light absorption range, low photo-generated charge recombination rate, and exhibit excellent photocatalytic reduction of carbon dioxide and photocatalytic oxidation of benzyl alcohol activity and good stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a titanium dioxide / cadmium zinc sulfide heterojunction hollow microsphere catalyst with zinc and oxygen double vacancies, a preparation method of the titanium dioxide / cadmium zinc sulfide heterojunction hollow microsphere catalyst with zinc and oxygen double vacancies and application of the titanium dioxide / cadmium zinc sulfide heterojunction hollow microsphere catalyst with zinc and oxygen double vacancies. BACKGROUND

[0002] In the past three centuries, the massive use of fossil fuels has led to the excessive emission of carbon dioxide, causing global warming and other climate and environmental changes. The conversion of carbon dioxide into fuels and valuable chemicals through photocatalytic reactions will be a very promising method to reduce the concentration of carbon dioxide in the atmosphere. Therefore, photocatalytic carbon dioxide reduction (PCR) can simultaneously solve the energy and environmental crises. Developing efficient and low-cost semiconductor photocatalysts is the key to improving the efficiency of PCR.

[0003] An ideal PCR photocatalyst requires strong light capture ability, light absorption ability, high redox potential, high charge separation efficiency, and strong binding strength of the reaction intermediates on the catalyst surface. In the past few decades, semiconductor materials such as titanium dioxide have dominated the field of photocatalysis. Semiconductor titanium dioxide, with a relatively suitable band gap, good photochemical stability, non-toxicity, rich morphology, and low price, is an ideal candidate for carbon dioxide reduction photocatalysts. However, the inherent defects of titanium dioxide, such as low solar energy utilization efficiency and rapid recombination of photo-generated electron-hole pairs, make it difficult to improve its photocatalytic activity efficiency. In recent years, researchers have proposed various strategies to improve the photocatalytic performance of titanium dioxide, including morphology control, element doping, cocatalyst loading, surface engineering, and construction of heterojunctions, etc. However, the PCR activity of titanium dioxide is still low. Therefore, multiple strategies need to be used to improve the performance of titanium dioxide.

[0004] In order to improve the efficiency of PCR and organic conversion of titanium dioxide, both thermodynamic and kinetic aspects need to be considered. First, a photocatalyst with high redox ability needs to be designed. Specifically, the electrons on the CB need to have sufficient reducing ability to reduce CO2 molecules. At the same time, the holes on the VB need to have sufficient oxidizing ability to achieve selective oxidation of organic substances. Second, in terms of kinetics, the following points should be considered: 1) high separation efficiency of photo-generated electrons and holes; 2) sufficient surface catalytic active sites; 3) good adsorption ability for reactants (CO2 and biomass-derived alcohol compounds) and easy desorption of target products. However, it is difficult to achieve all these goals for a single-component catalyst.

[0005] Therefore, in order to overcome the defects in the prior art, the application provides a catalyst of a hollow microsphere of a titanium dioxide / cadmium zinc sulfide heterojunction with zinc and oxygen double vacancies, a preparation method of the catalyst of the hollow microsphere of the titanium dioxide / cadmium zinc sulfide heterojunction with zinc and oxygen double vacancies, and an application of the catalyst of the hollow microsphere of the titanium dioxide / cadmium zinc sulfide heterojunction with zinc and oxygen double vacancies. SUMMARY

[0006] One of the purposes of the application is to provide a catalyst of a hollow microsphere of a titanium dioxide / cadmium zinc sulfide heterojunction with zinc and oxygen double vacancies to avoid the defects in the prior art. The catalyst of the hollow microsphere of the titanium dioxide / cadmium zinc sulfide heterojunction with zinc and oxygen double vacancies has high photocatalytic activity and cycle stability.

[0007] The above purposes of the application are achieved by the following technical measures.

[0008] The application provides a catalyst of a hollow microsphere of a titanium dioxide / cadmium zinc sulfide heterojunction with zinc and oxygen double vacancies. The hollow microsphere of the titanium dioxide / cadmium zinc sulfide heterojunction includes a substrate of an oxygen vacancy-containing titanium dioxide hollow microsphere and zinc vacancy-containing cadmium zinc sulfide nanoparticles grown on the surface of the titanium dioxide hollow microsphere, so as to form the hollow microsphere of the titanium dioxide / cadmium zinc sulfide heterojunction with zinc and oxygen double vacancies.

[0009] Preferably, the hollow microsphere of the titanium dioxide / cadmium zinc sulfide heterojunction is a TiO2 hollow microsphere containing oxygen vacancies loaded with Zn 0.28 Cd 0.72 S.

[0010] Preferably, the hollow microsphere of the titanium dioxide / cadmium zinc sulfide heterojunction is a hollow microsphere of a titanium dioxide / cadmium zinc sulfide Z-type heterojunction.

[0011] Preferably, the cadmium zinc sulfide nanoparticles are fixed on the surface of the titanium dioxide hollow microsphere.

[0012] Preferably, the average particle size of the cadmium zinc sulfide nanoparticles is 20 nm-30 nm.

[0013] Another purpose of the application is to provide a preparation method of a catalyst of a hollow microsphere of a titanium dioxide / cadmium zinc sulfide heterojunction with zinc and oxygen double vacancies to avoid the defects in the prior art. The preparation method of the catalyst of the hollow microsphere of the titanium dioxide / cadmium zinc sulfide heterojunction with zinc and oxygen double vacancies is a method of preparing double vacancy heterojunctions in situ by one-step hydrothermal method.

[0014] The above purposes of the application are achieved by the following technical measures.

[0015] Provided is a preparation method of a catalyst of a titanium dioxide / cadmium zinc sulfide heterojunction hollow microsphere, which is prepared by the following steps:

[0016] Step (1), synthesis of a titanium dioxide hollow microsphere;

[0017] Step (2), preparation of a titanium dioxide / cadmium zinc sulfide heterojunction hollow microsphere from the titanium dioxide hollow microsphere obtained in step (1).

[0018] Preferably, step (1) is specifically as follows:

[0019] Step (1.1), preparation of SiO2 microspheres by the stober method using tetraethyl orthosilicate and concentrated ammonia as main raw materials;

[0020] Step (1.2), preparation of amorphous titanium dioxide film-coated silica core-shell microspheres by a sol-gel combined with a heat treatment method using the SiO2 microspheres obtained in step (1.1), concentrated ammonia and tetrabutyl titanate as main raw materials;

[0021] Step (1.3), heating of the amorphous titanium dioxide film-coated silica core-shell microspheres obtained in step (1.2) to obtain anatase phase titanium dioxide film-coated silica core-shell microspheres.

[0022] Preferably, step (2) is specifically as follows:

[0023] Step (2.1), obtaining of etched microspheres by a sodium hydroxide etching method from the anatase phase titanium dioxide film-coated silica core-shell microspheres obtained in step (1);

[0024] Step (2.2), obtaining of titanium dioxide / cadmium zinc sulfide Z-type heterojunction hollow microspheres with zinc and oxygen double vacancies by an in-situ hydrothermal method using the etched microspheres obtained in step (2.1), zinc nitrate hexahydrate, cadmium nitrate hexahydrate and L-cysteine as main raw materials.

[0025] Preferably, step (1.1) is specifically as follows: 8-12 ml of tetraethyl orthosilicate (TEOS) and 80-120 ml of anhydrous ethanol are mixed to obtain solution A, 50-60 ml of deionized water, 80-120 ml of anhydrous ethanol and 15-20 ml of concentrated ammonia with a concentration of 22-28 wt% are mixed to obtain solution B, solution B is added to solution A at room temperature and reacted for 10-15 h, after the reaction is completed, centrifugal separation is performed, and the solid is washed alternately with deionized water and anhydrous ethanol, and dried to obtain SiO2 microspheres.

[0026] Preferably, the step (1.2) is specifically dispersing 0.2 g-0.6 g SiO2microspheres obtained in step (1.1) in 1 ml-3 ml 22 wt%-28 wt% concentrated ammonia water and 200 ml-300 ml anhydrous ethanol to obtain solution C; mixing 50 ml-100 ml anhydrous ethanol and 2 ml-4 ml tetrabutyl titanate to obtain solution D, then adding solution D to solution C, and reacting at 58 ℃-65 ℃ for 2 h-6 h, after the reaction is completed, centrifugal separation is performed, and the solid is washed alternately with deionized water and anhydrous ethanol, and dried to obtain amorphous titanium dioxide film-coated silica core-shell microspheres.

[0027] Preferably, the step (1.3) is specifically heating the amorphous titanium dioxide film-coated silica core-shell microspheres obtained in step (1.2) to 500 ℃-600 ℃ at a heating rate of 1 ℃ / min-5 ℃ / min, keeping for 1 h-3 h, and then cooling to room temperature to obtain anatase titanium dioxide film-coated silica core-shell microspheres.

[0028] Preferably, the step (2.1) is specifically ultrasonic dispersing the anatase titanium dioxide film-coated silica core-shell microspheres obtained in step (1) in 50 ml-100 ml 0.05 M-0.2 M sodium hydroxide solution, and reacting at a temperature of 85 ℃-95 ℃ for 2 h-6 h, after the reaction is completed, centrifugal separation is performed, and the solid is washed with deionized water, and dried to obtain etched microspheres.

[0029] Preferably, the step (2.2) is specifically ultrasonic dispersing all the etched microspheres obtained in step (2.1), 0.4 mmol-0.8 mmol zinc nitrate hexahydrate, 1.0 mmol-2.0 mmol cadmium nitrate hexahydrate and 3.0 mmol-6.0 mmol L-cysteine in 50 ml-100 ml deionized water to obtain a dispersion, then stirring for 0.5 h-2 h, after the stirring is completed, the dispersion is placed in a high-pressure reaction kettle, heated to 180 ℃-230 ℃, and kept for 15 h-20 h, then cooled to room temperature, the solid is separated, the solid is washed alternately with deionized water and anhydrous ethanol, and dried to obtain titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres.

[0030] Further preferably, the step (1.1) is specifically mixing 10 ml tetraethyl orthosilicate TEOS and 100 ml anhydrous ethanol to obtain solution A, mixing 55 ml deionized water, 100 ml anhydrous ethanol and 18 ml 28 wt% concentrated ammonia water to obtain solution B, adding solution B to solution A at room temperature, and reacting for 12 h, after the reaction is completed, centrifugal separation is performed, and the solid is washed alternately with deionized water and anhydrous ethanol, and dried to obtain SiO2microspheres.

[0031] Further preferably, step (1.2) is specifically that the 0.5 g of SiO2 microspheres obtained in step (1.1) is ultrasonically dispersed in 2 ml of 28 wt% concentrated ammonia water and 250 ml of anhydrous ethanol to obtain solution C; 80 ml of anhydrous ethanol and 3.4 ml of tetrabutyl titanate are mixed to obtain solution D, and then the solution D is added to the solution C, and the reaction is carried out at 60℃ for 4 h; after the reaction is completed, centrifugal separation is carried out, and the solid is washed alternately with deionized water and anhydrous ethanol, and dried to obtain the amorphous titanium dioxide film-coated silica core-shell microspheres.

[0032] Further preferably, step (1.3) is specifically that the amorphous titanium dioxide film-coated silica core-shell microspheres obtained in step (1.2) are heated to 550℃ at a heating rate of 3℃ / min, and kept for 2 h, and then cooled to room temperature to obtain the anatase titanium dioxide film-coated silica core-shell microspheres.

[0033] Further preferably, step (2.1) is specifically that the anatase titanium dioxide film-coated silica core-shell microspheres obtained in step (1) are ultrasonically dispersed in 80 ml of 0.1M sodium hydroxide solution, and reacted at a temperature of 90℃ for 4 h; after the reaction is completed, centrifugal separation is carried out, and the solid is washed with deionized water, and dried to obtain the etched microspheres.

[0034] Further preferably, step (2.2) is specifically that all the etched microspheres obtained in step (2.1), 0.6 mmol of zinc nitrate hexahydrate, 1.4 mmol of cadmium nitrate hexahydrate and 4.0 mmol of L-cysteine are ultrasonically dispersed in 60 ml of deionized water to obtain a dispersion, and then stirred for 1 h; after the stirring is completed, the dispersion is placed in a high-pressure reaction kettle, heated to 200℃, and kept for 18 h, and then cooled to room temperature; the solid is separated, washed alternately with deionized water and anhydrous ethanol, and dried to obtain the titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres.

[0035] Another object of the present application is to provide the application of the titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres with zinc and oxygen double vacancies as a photocatalyst in solar energy conversion, so as to avoid the defects of the prior art.

[0036] The above object of the present application is achieved by the following technical measures:

[0037] The application provides a catalyst of a titanium dioxide / cadmium zinc sulfide heterojunction hollow microsphere with zinc and oxygen double vacancies as a photocatalyst in solar energy conversion, and the titanium dioxide / cadmium zinc sulfide heterojunction hollow microsphere is as claimed in any one of claims 1 to 4.

[0038] or

[0039] The titanium dioxide / cadmium zinc sulfide heterojunction hollow microsphere is prepared by the preparation method of the catalyst of the titanium dioxide / cadmium zinc sulfide heterojunction hollow microsphere with zinc and oxygen double vacancies as claimed in any one of claims 5 to 8.

[0040] The catalyst catalyzes a carbon dioxide reduction reaction.

[0041] or

[0042] The catalyst catalyzes a selective oxidation reaction of benzyl alcohol.

[0043] The application has the following beneficial effects:

[0044] 1. The catalyst of the titanium dioxide / cadmium zinc sulfide heterojunction hollow microsphere with zinc and oxygen double vacancies has a zinc and oxygen double vacancy structure, and has the characteristics of high stability of titanium dioxide and high solar energy utilization efficiency of cadmium zinc sulfide; the titanium dioxide nanoparticles are constructed into a hollow sphere, so that the disadvantages of poor photocatalytic activity and small specific surface area of the titanium dioxide nanoparticles are solved; the porous thin shell layer of the titanium dioxide hollow microsphere can effectively shorten the diffusion path of photo-generated carriers and realize rapid mass transfer; and the cadmium zinc sulfide greatly expands the light absorption range of the composite material and provides a large number of active sites.

[0045] 2. The catalyst not only solves the shortcomings of insufficient oxidation and reduction capacity of a single-component catalyst, but also effectively avoids the recombination of photo-generated electrons and holes; and simultaneously improves the cycle stability of the photocatalyst. The catalyst significantly increases the active sites, improves the adsorption of the composite material to reactants, and the defect sites can also be used as trapping sites to trap photoexcited electrons or holes, so that the carriers are separated.

[0046] 3. The application is synthesized by in-situ hydrothermal synthesis, that is, oxygen vacancies and zinc vacancies are constructed on two units of the heterojunction in the process of forming the heterojunction, so that the preparation method is simple.

[0047] 4、The catalyst can form high-catalytic-activity solar energy conversion material, realize the fixation of solar energy, and slow down the aggregation of nanoparticles in the photocatalytic reaction process. In the catalyst, light can be scattered on the hollow sphere for multiple times, which is beneficial to the capture of light. The thin shell layer of titanium dioxide reduces the transmission distance of charge carriers, inhibits the recombination of photo-generated charges, and realizes fast mass transfer and provides highly accessible surface positions due to the large specific surface area of the porous shell layer of the hollow microspheres of titanium dioxide, thereby accelerating the surface / interface reaction. In addition, the cadmium zinc sulfide in the catalyst greatly improves the light response range of the composite material, which is beneficial to improving the solar energy utilization rate, and the Z-type heterojunction formed by the two greatly promotes the photocatalytic redox capacity and the cycle stability. The vacancies on the surfaces of titanium dioxide and cadmium zinc sulfide are also beneficial to the surface / interface reaction. The obtained material has high photocatalytic activity and good cycle stability. BRIEF DESCRIPTION OF DRAWINGS

[0048] The application will be further described with reference to the accompanying drawings, but the content in the drawings does not constitute any limitation on the application.

[0049] Figure 1 It is a structure schematic diagram of the titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres of the application, wherein (1) is a cadmium zinc sulfide nanoparticle, and (2) is a titanium dioxide hollow microsphere.

[0050] Figure 2 It is a preparation process flow chart of the titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres of the application. In the chart, 1 is a silica microsphere, 2 is anatase phase titanium dioxide film-coated silica core-shell microsphere, 3 is an anatase phase titanium dioxide hollow microsphere, and 4 is a titanium dioxide / cadmium zinc sulfide heterojunction hollow microsphere containing zinc and oxygen double vacancies; A is a sol-gel combined heat treatment method, B is a sodium hydroxide etching method, and C is an in-situ hydrothermal method.

[0051] Figure 3 It is an X-ray diffraction chart of the titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres of the application.

[0052] Figure 4 It is a transmission electron microscope chart of the anatase phase titanium dioxide hollow microsphere, the cadmium zinc sulfide nanoparticle, and the titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres of the application, wherein Figure 4 (a) and Figure 4 ((b) is a transmission electron microscope chart of the anatase phase titanium dioxide hollow microsphere at different magnifications; Figure 4 (c) and Figure 4 (d) is a transmission electron microscope chart of the cadmium zinc sulfide nanoparticle at different magnifications; Figure 4 (e) and Figure 4(f) are transmission electron microscopy images of the inventive hollow titania / cadmium zinc sulfide heterojunction microspheres at different magnifications.

[0053] Figure 5 are electron paramagnetic resonance spectra of anatase titania hollow microspheres, oxygen-vacancy-containing titania hollow microspheres, cadmium zinc sulfide nanoparticles and the inventive hollow titania / cadmium zinc sulfide heterojunction microspheres.

[0054] Figure 6 are high-resolution X-ray photoelectron spectra of the inventive hollow titania / cadmium zinc sulfide heterojunction microspheres.

[0055] Figure 7 are steady-state fluorescence spectra of anatase titania hollow microspheres, oxygen-vacancy-containing titania hollow microspheres, cadmium zinc sulfide nanoparticles and the inventive hollow titania / cadmium zinc sulfide heterojunction microspheres.

[0056] Figure 8 are ultraviolet-visible diffuse reflectance spectra of silica@anatase titania core-shell microspheres, anatase titania hollow microspheres, oxygen-vacancy-containing titania hollow microspheres, cadmium zinc sulfide nanoparticles and the inventive hollow titania / cadmium zinc sulfide heterojunction microspheres.

[0057] Figure 9 are photocatalytic activities of anatase titania hollow microspheres, oxygen-vacancy-containing titania hollow microspheres, cadmium zinc sulfide nanoparticles and the inventive hollow titania / cadmium zinc sulfide heterojunction microspheres, wherein Figure 9 (a) is photocatalytic oxidation of benzyl alcohol; Figure 9 (b) is selectivity of photocatalytic oxidation of benzyl alcohol; Figure 9 (c) is photocatalytic reduction of carbon dioxide activity; Figure 9 (d) is selectivity of photocatalytic reduction products.

[0058] Figure 10 are cyclic stability tests of the inventive hollow titania / cadmium zinc sulfide heterojunction microspheres. DETAILED DESCRIPTION

[0059] The technical solutions of the present application are further illustrated in combination with the following examples. In the following examples, the experimental methods are all conventional methods unless otherwise specified. In the following examples, the raw materials, reagents and materials used are all commercially available from conventional biochemical reagent stores or pharmaceutical business enterprises unless otherwise specified.

[0060] Example 1

[0061] A catalyst of a hollow titania / cadmium zinc sulfide heterojunction microsphere with zinc and oxygen double vacancies, such as Figure 1As shown, the titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres include a substrate of oxygen vacancy-containing titanium dioxide hollow microspheres and zinc vacancy-containing cadmium zinc sulfide nanoparticles grown on the surface of the titanium dioxide hollow microspheres, thereby forming the titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres with zinc and oxygen double vacancies. The cadmium zinc sulfide nanoparticles are anchored on the surface of the titanium dioxide hollow microspheres and are closely connected to each other, and the mesopores are uniformly distributed on the surface of the titanium dioxide hollow microspheres. The average particle size of the cadmium zinc sulfide nanoparticles of the present application is 20-30 nm.

[0062] It should be noted that titanium dioxide is widely used due to its low cost, non-toxicity, high stability and activity, and easy preparation, etc. In particular, the titanium dioxide hollow microspheres with large specific surface area, thin shell, and rich mesopores are used as a substrate material to grow visible light photocatalysts, which can effectively improve the separation efficiency of photo-generated carriers, the light response range, and the redox capacity, and has broad application prospects in the field of solar energy conversion materials.

[0063] The titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres are TiO2 hollow microspheres loaded with Zn 0.28 Cd 0.72 S, and the titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres are titanium dioxide / cadmium zinc sulfide Z-type heterojunction hollow microspheres.

[0064] The preparation method of the catalyst of the titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres of the present application is as follows: Figure 2 As shown, the catalyst is prepared by the following steps:

[0065] Step (1), synthesis of titanium dioxide hollow microspheres;

[0066] Step (2), preparation of titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres from the titanium dioxide hollow microspheres obtained in step (1).

[0067] Specifically, step (1) is as follows:

[0068] Step (1.1), preparation of SiO2 microspheres by stober method using tetraethyl orthosilicate and concentrated ammonia as main raw materials;

[0069] Step (1.2), preparation of amorphous titanium dioxide film-coated silica core-shell microspheres by sol-gel combined with heat treatment method using the SiO2 microspheres obtained in step (1.1), concentrated ammonia, and tetrabutyl titanate as main raw materials;

[0070] Step (1.3), heating of the amorphous titanium dioxide film-coated silica core-shell microspheres obtained in step (1.2) to obtain anatase titanium dioxide film-coated silica core-shell microspheres.

[0071] Step (2) is as follows:

[0072] Step (2.1), etching microspheres are obtained by etching the anatase phase titanium dioxide film coated silica core-shell microspheres obtained in step (1) through a sodium hydroxide etching method;

[0073] Step (2.2), the etching microspheres obtained in step (2.1), zinc nitrate hexahydrate, cadmium nitrate hexahydrate and L-cysteine are used as main raw materials to obtain titanium dioxide / cadmium zinc sulfide Z-type heterojunction hollow microspheres with zinc and oxygen double vacancies through an in-situ hydrothermal method.

[0074] In step (1.1), 8 ml of tetraethyl orthosilicate (TEOS) and 80 ml of anhydrous ethanol are mixed to obtain solution A, 50 ml of deionized water, 80 ml of anhydrous ethanol and 15 ml of concentrated ammonia water with a concentration of 25 wt% are mixed to obtain solution B, solution B is added to solution A at room temperature and reacted for 10 h, after the reaction is completed, centrifugal separation is performed, and the solid is washed alternately with deionized water and anhydrous ethanol, and then dried to obtain SiO2 microspheres, wherein the solid needs to be washed alternately with deionized water and anhydrous ethanol for three times in the step of washing the solid.

[0075] In step (1.2), 0.2 g of SiO2 microspheres obtained in step (1.1) are ultrasonically dispersed in 1 ml of 25 wt% concentrated ammonia water and 200 ml of anhydrous ethanol to obtain solution C, 50 ml of anhydrous ethanol and 2 ml of tetrabutyl titanate are mixed to obtain solution D, and then solution D is added to solution C and reacted at 58°C for 2 h, after the reaction is completed, centrifugal separation is performed, and the solid is washed alternately with deionized water and anhydrous ethanol, and then dried to obtain amorphous titanium dioxide film coated silica core-shell microspheres, wherein the solid needs to be washed alternately with deionized water and anhydrous ethanol for three times in the step of washing the solid.

[0076] In step (1.3), the amorphous titanium dioxide film coated silica core-shell microspheres obtained in step (1.2) are heated to 500°C at a heating rate of 1°C / min, and then kept at this temperature for 1 h, and then cooled to room temperature to obtain anatase phase titanium dioxide film coated silica core-shell microspheres.

[0077] In step (2.1), the anatase phase titanium dioxide film coated silica core-shell microspheres obtained in step (1) are ultrasonically dispersed in 50 ml of 0.05M sodium hydroxide solution, and reacted at a temperature of 85°C for 2 h, after the reaction is completed, centrifugal separation is performed, and the solid is washed with deionized water, and then dried to obtain etching microspheres, wherein the solid needs to be washed with deionized water for three times in the step of washing the solid.

[0078] In step (2.2), the whole etching microspheres, 0.4 mmol zinc nitrate hexahydrate, 1.0 mmol cadmium nitrate hexahydrate and 3.0 mmol L-cysteine obtained in step (2.1) are ultrasonically dispersed in 50 m deionized water to obtain a dispersion, then stirred for 0.5 h, after stirring, the dispersion is placed in a high-pressure reaction kettle, heated to 180℃, and kept for 15 h, then cooled to room temperature, the solid is separated, the solid is washed with deionized water and anhydrous ethanol alternately, and dried to obtain titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres, wherein the solid needs to be washed with deionized water and anhydrous ethanol alternately for three times in the step of washing the solid.

[0079] In order to improve the efficiency of the PCR and organic conversion of titanium dioxide, the present application considers both thermodynamics and kinetics. First, a photocatalyst with high redox ability needs to be designed. Specifically, the electrons on the CB need to have sufficient reducing ability to reduce CO2 molecules. At the same time, the holes on the VB need to have sufficient oxidizing ability to achieve selective oxidation of organic matter. Secondly, in terms of kinetics, the following points should be considered: 1) high separation efficiency of photo-generated electrons and holes; 2) sufficient surface catalytic active sites; 3) good adsorption ability for reactants (CO2 and biomass-derived alcohol compounds) and easy desorption of target products. However, it is difficult for a single-component catalyst to achieve all these goals. In order to improve the redox ability of the photocatalyst, building a ladder-type or Z-type heterojunction is considered to be one of the most promising methods. The reason is that the strong photo-generated electrons and holes can be retained in the two semiconductors respectively, accelerating the recombination of free photo-generated carriers, thereby endowing the heterojunction structure with strong redox ability. Photocatalytic oxidation and reduction reactions occur on different semiconductor surfaces. At the same time, the spatial separation of photo-generated electrons and holes is also enhanced in this system. It is well known that photocatalytic reactions generally occur at liquid-solid or gas-solid interfaces. Therefore, the interface activation or modification of the photocatalyst is of great significance to improve the photocatalytic performance. Previous studies have shown that semiconductor surface vacancy engineering plays a crucial role in the adsorption and activation of CO2 in the photocatalytic process. The vacancies in the semiconductor can introduce new defect energy levels in the band gap, thereby narrowing the band gap and significantly expanding the optical response region. Defect sites can also act as trapping sites to capture photo-generated electrons and holes, thereby achieving carrier separation.

[0080] The principle of the titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres with zinc and oxygen double vacancies of the present application is as follows: (1) the adsorption and activation of CO2 on the photocatalyst are improved by creating oxygen vacancies and zinc vacancies on the surfaces of titanium dioxide and cadmium zinc sulfide, respectively; (2) the redox capacity of the photocatalyst is enhanced by constructing a Z-type heterojunction; and (3) the light trapping efficiency of the photocatalyst is improved by constructing a hollow structure. The present application is characterized in that the double vacancy heterojunction is synthesized by a cleverly designed in-situ hydrothermal method, which improves the photocatalytic efficiency in terms of thermodynamics and kinetics. At the same time, the defects of insufficient redox capacity of a single catalyst and low adsorption and activation efficiency of CO2 and other reactants are solved.

[0081] Specifically, the titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres of the present application have cadmium zinc sulfide nanoparticles directly grown on the surface of the porous titanium dioxide hollow microspheres. In this process, vacancy defects appear on the surfaces of both, forming a high-catalytic-activity solar energy conversion material and realizing the fixation of solar energy. The presence of the titanium dioxide hollow microspheres provides favorable support for the cadmium zinc sulfide nanoparticles, which can slow down the aggregation of the nanoparticles in the process of photocatalysis. Light can be scattered multiple times on the hollow spheres, which is conducive to the capture of light. The thin shell layer of titanium dioxide reduces the transmission distance of charge carriers and inhibits the recombination of photo-generated charges. The porous shell layer of the titanium dioxide hollow microspheres has a large specific surface area, realizes fast mass transfer, and provides highly accessible surface sites to accelerate surface / interface reactions. In addition, the cadmium zinc sulfide greatly improves the light response range of the composite material, which is conducive to improving the utilization rate of solar energy.

[0082] Moreover, the Z-type heterojunction formed by titanium dioxide and cadmium zinc sulfide greatly promotes the photocatalytic redox capacity and cycle stability. The vacancy defects on the surfaces of titanium dioxide and cadmium zinc sulfide are also conducive to surface / interface reactions. The obtained material has high photocatalytic activity and good cycle stability.

[0083] In the prior art, vacancy defects are constructed on the surface of a semiconductor by methods such as hydrogen heat treatment, high-energy particle bombardment, metal or non-metal ion doping, and heat treatment in an inert gas atmosphere. It can be found that these methods have high energy consumption, are not environmentally friendly, and have certain radiation hazards. The preparation method of the present application is to synthesize a double vacancy heterojunction by in-situ hydrothermal synthesis, that is, to construct oxygen vacancies and zinc vacancies on the two units of the heterojunction during the formation of the heterojunction. Specifically, L-cysteine is used as a sulfuration agent and a vacancy formation aid in the present application. During the hydrothermal reaction, L-cysteine reduces the tetravalent titanium of titanium dioxide to trivalent titanium and generates oxygen vacancies; at the same time, L-cysteine is also an aid for the formation of zinc vacancies of cadmium zinc sulfide. This discovery provides a more reasonable and efficient path for the synthesis of double vacancy heterojunctions, especially transition metal oxide / transition metal sulfide heterojunctions.

[0084] The titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres of the application have the characteristics of high stability of titanium dioxide and high solar energy utilization efficiency of cadmium zinc sulfide, the titanium dioxide nanoparticles are constructed into hollow spheres, the disadvantages of poor photocatalytic activity and small specific surface area of the titanium dioxide nanoparticles are solved, the porous thin shell layer of the titanium dioxide hollow microspheres can effectively shorten the diffusion path of the photo-generated carriers and realize rapid mass transfer, the cadmium zinc sulfide greatly expands the light absorption range of the composite material and provides a large number of active sites. The Z-type heterojunction formed between the titanium dioxide and the cadmium zinc sulfide not only solves the shortcomings of insufficient redox ability of the single-component catalyst, but also effectively avoids the recombination of the photo-generated electron-hole pairs. At the same time, the Z-type heterojunction formed solves the disadvantage of easy photo-corrosion of the cadmium zinc sulfide, and improves the cycle stability of the photocatalyst. At the same time of constructing the Z-type heterojunction, the vacancies introduced on the surfaces of different components of the composite material significantly increase the active sites to improve the adsorption of the reactants by the composite material, and the defect sites can also act as trapping sites to trap the photo-excited electrons or holes, so as to separate the carriers.

[0085] The zinc, oxygen double vacancy titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres of the application have the strong photocatalytic oxidation ability, large specific surface area and porosity of the titanium dioxide hollow microspheres, and the visible light response and strong photocatalytic reduction ability of the cadmium zinc sulfide nanoparticles. At the same time, the oxygen vacancies and zinc vacancies constructed on the surfaces of the titanium dioxide and the cadmium zinc sulfide respectively are beneficial to improving the adsorption performance of the composite material on carbon dioxide, adjusting the band gap and increasing the active sites. Therefore, the titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres can be used as a solar energy conversion material to convert solar energy into chemical energy.

[0086] Example 2

[0087] A catalyst with a zinc, oxygen double vacancy titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres, other features are the same as example 1, the difference is that:

[0088] Step (1.1) is specifically to mix 12 ml of tetraethyl orthosilicate TEOS and 120 ml of anhydrous ethanol to obtain solution A, mix 60 ml of deionized water, 120 ml of anhydrous ethanol and 20 ml of concentrated ammonia water with a concentration of 28wt% to obtain solution B, add solution B to solution A at room temperature and react for 15h, after the reaction is completed, centrifugal separation is performed, and the solid is washed alternately with deionized water and anhydrous ethanol, and dried to obtain SiO2 microspheres, wherein the solid needs to be washed alternately with deionized water and anhydrous ethanol for three times in the step of washing the solid.

[0089] Step (1.2) is specifically dispersing 0.6 g of the SiO2 microspheres obtained in step (1.1) in 3 ml of 28 wt% concentrated ammonia water and 300 ml of anhydrous ethanol to obtain solution C; mixing 100 ml of anhydrous ethanol and 4 ml of tetrabutyl titanate to obtain solution D, then adding solution D to solution C, and reacting at 65°C for 6 h; after the reaction is completed, centrifugal separation is performed, and the solid is washed alternately with deionized water and anhydrous ethanol three times, and then dried to obtain the amorphous titanium dioxide film-coated silica core-shell microspheres.

[0090] Step (1.3) is specifically heating the amorphous titanium dioxide film-coated silica core-shell microspheres obtained in step (1.2) to 600°C at a temperature increasing rate of 5°C / min, maintaining the temperature for 3 h, and then cooling to room temperature to obtain the anatase titanium dioxide film-coated silica core-shell microspheres.

[0091] Step (2.1) is specifically dispersing the anatase titanium dioxide film-coated silica core-shell microspheres obtained in step (1) in 100 ml of 0.2M sodium hydroxide solution, and reacting at a temperature of 95°C for 6 h; after the reaction is completed, centrifugal separation is performed, and the solid is washed with deionized water three times, and then dried to obtain the etched microspheres.

[0092] Step (2.2) is specifically dispersing all the etched microspheres obtained in step (2.1), 0.8 mmol of zinc nitrate hexahydrate, 1.0 mmol of cadmium nitrate hexahydrate, and 6.0 mmol of L-cysteine in 50 ml of deionized water to obtain a dispersion, then stirring for 2.0 h; after the stirring is completed, the dispersion is placed in a high-pressure reaction kettle, heated to 230°C, and maintained at this temperature for 20 h, then cooled to room temperature, the solid is separated, and the solid is washed alternately with deionized water and anhydrous ethanol three times, and then dried to obtain the titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres.

[0093] Example 3

[0094] A catalyst for a titanium dioxide / cadmium zinc sulfide heterojunction hollow microsphere with zinc and oxygen double vacancies, other features being the same as in Example 1, except that:

[0095] Step (1.1) is specifically mixing 10 ml of tetraethyl orthosilicate (TEOS) and 100 ml of anhydrous ethanol to obtain solution A, mixing 55 ml of deionized water, 100 ml of anhydrous ethanol and 18 ml of concentrated ammonia water with a concentration of 28 wt% to obtain solution B, adding solution B to solution A at room temperature and reacting for 12 h, centrifugally separating after the reaction is completed, and alternately washing the solid with deionized water and anhydrous ethanol three times in the step of washing the solid, and drying to obtain SiO2 microspheres.

[0096] Step (1.2) is specifically ultrasonically dispersing 0.5 g of the SiO2 microspheres obtained in step (1.1) in 2 ml of 28 wt% concentrated ammonia water and 250 ml of anhydrous ethanol to obtain solution C, mixing 80 ml of anhydrous ethanol and 3.4 ml of tetrabutyl titanate to obtain solution D, then adding solution D to solution C, and reacting at 60°C for 4 h, centrifugally separating after the reaction is completed, and alternately washing the solid with deionized water and anhydrous ethanol three times in the step of washing the solid, and drying to obtain amorphous titanium dioxide film-coated silica core-shell microspheres.

[0097] Step (1.3) is specifically heating the amorphous titanium dioxide film-coated silica core-shell microspheres obtained in step (1.2) to 550°C at a heating rate of 3°C / min, maintaining the temperature for 2 h, and then cooling to room temperature to obtain anatase titanium dioxide film-coated silica core-shell microspheres.

[0098] Step (2.1) is specifically ultrasonically dispersing the anatase titanium dioxide film-coated silica core-shell microspheres obtained in step (1) in 80 ml of 0.1M sodium hydroxide solution, and reacting at a temperature of 90°C for 4 h, centrifugally separating after the reaction is completed, and washing the solid with deionized water three times in the step of washing the solid, and drying to obtain etched microspheres.

[0099] Step (2.2) is specifically ultrasonically dispersing all of the etched microspheres obtained in step (2.1), 0.6 mmol of zinc nitrate hexahydrate, 1.4 mmol of cadmium nitrate hexahydrate and 4.0 mmol of L-cysteine in 60 ml of deionized water to obtain a dispersion, then stirring for 1 h, placing the dispersion in a high-pressure reaction kettle after the stirring is completed, heating to 200°C, maintaining the temperature for 18 h, then cooling to room temperature, separating the solid, alternately washing the solid with deionized water and anhydrous ethanol three times in the step of washing the solid, and drying to obtain titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres.

[0100] Detection and analysis

[0101] 1. X-ray diffraction pattern characterization

[0102] The titanium dioxide / cadmium sulfide zinc heterostructure hollow microspheres obtained in Example 3 were characterized by X-ray diffraction patterns, such as... Figure 3 The titanium dioxide / cadmium sulfide zinc heterostructure hollow microspheres prepared in Examples 1 and 2 yielded the following results: Figure 3 The same graphs will not be shown here one by one.

[0103] from Figure 3 As can be seen, there is a distinct crystal peak at 2θ = 25.2–55.2°, belonging to anatase titanium dioxide (JCPDS No. 21-1272). Diffraction peaks at 2θ = 25.50, 27.08, 28.78, 37.44, 44.83, 48.90, 52.23, and 55.70° confirm the presence of zinc cadmium sulfide (JCPDS No. 40-0836). XRD results indicate that the modification with zinc cadmium sulfide did not alter the crystal structure of titanium dioxide and zinc cadmium sulfide.

[0104] 2. Structural characterization

[0105] The titanium dioxide / cadmium sulfide zinc heterojunction hollow microspheres obtained in Example 3 were structurally characterized, such as... Figure 4 The titanium dioxide / cadmium sulfide zinc heterostructure hollow microspheres prepared in Examples 1 and 2 yielded the following results: Figure 4 The same graphs will not be shown here one by one.

[0106] exist Figure 4 In Figure 4 a and 4b are transmission electron microscope (TEM) images of anatase phase titanium dioxide hollow microspheres at different magnifications; 4c and 4d are TEM images of zinc cadmium sulfide nanoparticles at different magnifications; and 4e and 4f are TEM images of zinc- and oxygen-containing double-vacancy titanium dioxide / zinc cadmium sulfide heterostructure hollow microspheres at different magnifications.

[0107] from Figure 4 Figures a and 4b show that after etching the core silicon dioxide with sodium hydroxide, the titanium dioxide exhibits a hollow structure and numerous mesopores appear on the shell surface, which is likely due to the sodium hydroxide etching. The 0.352 nm lattice fringes correspond to the (101) plane of TiO2.

[0108] from Figure 4 c and 4d show that zinc cadmium sulfide is granular with an average diameter of about 20-30 nm, and 0.312 nm lattice stripes correspond to the (101) plane of zinc cadmium sulfide.

[0109] from Figure 4e shows that the CdSZ nanoparticles are uniformly anchored on the surface of the Ti02 hollow microspheres. The Ti02 hollow microspheres modified by CdSZ nanoparticles still maintain the special hollow structure, indicating that there is a close interface contact between the CdSZ nanoparticles and the Ti02 hollow microspheres.

[0110] From Figure 4 f shows that the (101) plane of CdSZ corresponds to a lattice fringe of 0.312 nm and the (101) plane of Ti02 corresponds to a lattice fringe of 0.352 nm, both of which are easily observed, which is consistent with the results of X-ray diffraction. These results prove the successful introduction of CdSZ nanoparticles on the Ti02 hollow microspheres and the successful construction of the Ti02 / CdSZ heterojunction.

[0111] 3. Structure characterization

[0112] The Ti02 / CdSZ heterojunction hollow microspheres obtained in Example 3 were subjected to structure characterization, specifically electron paramagnetic resonance spectrograms, as shown in Figure 5 The Ti02 / CdSZ heterojunction hollow microspheres obtained in Examples 1 and 2 were subjected to structure characterization, specifically electron paramagnetic resonance spectrograms, as shown in Figure 5 The same spectrograms are not shown one by one here.

[0113] From Figure 5 It can be seen that the spectrogram of the Ti02 hollow microspheres without oxygen vacancies is almost a smooth line. In contrast, the Ti02 / CdSZ heterojunction hollow microspheres with zinc and oxygen double vacancies exhibit a strong EPR peak due to the detection of single free electrons in the sample, confirming the existence of a large number of vacancy defects on the surface of the Ti02 / CdSZ heterojunction hollow microspheres with zinc and oxygen double vacancies.

[0114] In order to confirm the type of surface defects and the mechanism of vacancy formation, under the same conditions as Example 3 except for the control variable (no CdSZ, no zinc nitrate and cadmium nitrate to obtain Ti02 with oxygen vacancies), the EPR spectrograms of Ti02 with oxygen vacancies and CdSZ were obtained.

[0115] In the figure, ZCS exhibits a strong EPR peak at g = 2.002, indicating the existence of vacancy defects on ZCS corresponding to zinc vacancies. The Ti02 hollow microspheres with oxygen vacancies exhibit a strong EPR peak at g = 2.002, confirming the existence of oxygen vacancies on the surface, indicating that during the hydrothermal reaction process, L-cysteine not only acts as a sulfur source, but also acts as a reducing agent, causing the Ti02 to be slightly reduced, resulting in the loss of oxygen atoms. Compared with the Ti02 hollow microspheres with oxygen vacancies and CdSZ, the EPR peak of the Ti02 / CdSZ heterojunction hollow microspheres with zinc and oxygen double vacancies is different, both the peak intensity and position change, indicating the existence of double vacancies.

[0116] 4. X-ray photoelectron spectroscopy characterization

[0117] X-ray photoelectron spectroscopy (XPS) was performed on the titanium dioxide / cadmium sulfide zinc heterostructure hollow microspheres obtained in Example 3, specifically high-resolution XPS of the Ti 2p orbitals. Figure 6 The titanium dioxide / cadmium sulfide zinc heterostructure hollow microspheres prepared in Examples 1 and 2 yielded the following results: Figure 6 The same graphs will not be shown here one by one.

[0118] like Figure 6 As shown, the high-resolution X-ray photoelectron spectrum of the Ti 2p orbitals of the titanium dioxide / cadmium sulfide zinc heterostructure hollow microspheres has four distinct peaks, with the peaks at 458.6 and 464.2 eV attributed to Ti. 4+ The peaks at 456.2 and 461.4 eV correspond to Ti. 3+ The presence of [something]. In defect-free titanium dioxide, the oxidation state of titanium should be +4, Ti [something]. 3+ The presence of oxygen atoms indicates a decrease in the coordination number of titanium atoms and a lack of oxygen atoms, further proving that the sample contains oxygen vacancies.

[0119] 5. Steady-state fluorescence spectroscopy characterization

[0120] The titanium dioxide / cadmium sulfide zinc heterostructure hollow microspheres obtained in Example 3 were characterized by steady-state fluorescence spectroscopy, such as... Figure 7 The titanium dioxide / cadmium sulfide zinc heterostructure hollow microspheres prepared in Examples 1 and 2 yielded the following results: Figure 7 The same graphs will not be shown here one by one.

[0121] in Figure 7 Yes, steady-state fluorescence spectra of anatase phase titanium dioxide hollow microspheres, oxygen-vacancy titanium dioxide hollow microspheres, zinc cadmium sulfide nanoparticles, and zinc- and oxygen-double-vacancy titanium dioxide / zinc cadmium sulfide heterojunction hollow microspheres.

[0122] from Figure 7It can be seen that the light-induced electron-hole separation ability of the samples is tested by steady-state fluorescence spectrum. Compared with the anatase titanium dioxide hollow microspheres, the emission intensity of the oxygen vacancy-containing titanium dioxide hollow microspheres is obviously reduced, indicating that the oxygen vacancy can effectively improve the separation efficiency of the photo-generated carriers. The defect sites can act as capture sites for capturing photo-generated electrons or holes to separate the carriers. The emission intensity of the zinc and oxygen double vacancy-containing titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres is much lower than that of the oxygen vacancy-containing titanium dioxide hollow microspheres and the zinc vacancy-containing cadmium zinc sulfide. The above indicates that due to the synergistic effect of the vacancy effect and the heterojunction, the photo-induced electron-hole recombination in the zinc and oxygen double vacancy-containing titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres is effectively inhibited. Therefore, more photo-induced electrons and holes are transferred to participate in the cooperative reaction of photocatalytic reduction of carbon dioxide and selective oxidation of benzyl alcohol, which is consistent with the photocatalytic performance of the zinc and oxygen double vacancy-containing titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres.

[0123] 6. UV-Vis diffuse reflectance spectrum characterization

[0124] The titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres obtained in Example 3 are subjected to UV-Vis diffuse reflectance spectrum characterization, as shown in Figure 8 The titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres obtained in Examples 1 and 2 are subjected to UV-Vis diffuse reflectance spectrum characterization, as shown in Figure 8 The same spectrum is not shown one by one here.

[0125] Specifically, Figure 8 UV-Vis diffuse reflectance spectra of the silica@anatase titanium dioxide core-shell microspheres, the anatase titanium dioxide hollow microspheres, the oxygen vacancy-containing titanium dioxide hollow microspheres, the cadmium zinc sulfide nanoparticles and the zinc and oxygen double vacancy-containing titanium dioxide / cadmium zinc sulfide heterojunction hollow microspheres.

[0126] From Figure 8It can be seen that the absorption band edges of the silica@anatase TiO2 core-shell microspheres, the anatase TiO2 hollow microspheres, the oxygen vacancy-containing TiO2 hollow microspheres, the CdZnS nanoparticles and the zinc and oxygen double vacancy-containing TiO2 / CdZnS heterojunction hollow microspheres are 385 nm, 395 nm, 401 nm, 525 nm and 511 nm, respectively. The band edge absorption of the silica@anatase TiO2 core-shell microspheres, the anatase TiO2 hollow microspheres and the oxygen vacancy-containing TiO2 hollow microspheres increases in turn, indicating that the light trapping ability is improved. The improvement of the light trapping ability of the anatase TiO2 hollow microspheres is mainly due to the light scattering effect. The oxygen vacancies in the oxygen vacancy-containing TiO2 hollow microspheres can introduce new defect energy levels in the band gap, thereby narrowing the band gap and expanding the light response region. However, the above-mentioned samples have almost no absorption ability in the visible light region. Notably, the addition of CdZnS widens the visible light range, which indicates that the zinc and oxygen double vacancy-containing TiO2 / CdZnS heterojunction hollow microspheres have good visible light response and can be used as a promising solar-driven material for photocatalytic reactions.

[0127] Example 4

[0128] The application of a catalyst of a titanium dioxide / CdZnS heterojunction hollow microsphere with zinc and oxygen double vacancies as a photocatalyst in solar energy conversion, wherein the titanium dioxide / CdZnS heterojunction hollow microsphere of the present example is the titanium dioxide / CdZnS heterojunction hollow microsphere of examples 1 to 3. The present application uses the titanium dioxide / CdZnS heterojunction hollow microsphere as a catalyst to catalyze the reduction reaction of carbon dioxide and the selective oxidation reaction of benzyl alcohol.

[0129] The photocatalytic oxidation of benzyl alcohol is the basis of the synergistic catalytic system, because benzyl alcohol has two important roles: a proton donor and a hole-trapping agent. First, the photocatalytic oxidation of benzyl alcohol also generates benzaldehyde and protons in a molar ratio of 1:2, as shown in equation (3). Subsequently, the protons participate in the photocatalytic reduction reaction, as shown in equations (1) and (2). Therefore, the upper limit of the photocatalytic reduction efficiency is determined by the photocatalytic oxidation activity of the synergistic catalytic system.

[0130] CO2+2H + +2e - →CO+H2O equation (1)

[0131] 2H + +2e - →H2 equation (2)

[0132]

[0133] Meanwhile, the present example uses the titanium dioxide / CdZnS heterojunction hollow microsphere as a catalyst to catalyze the reduction reaction of carbon dioxide and the selective oxidation reaction of benzyl alcohol. Figure 9The benzaldehyde production rate is shown, wherein the benzaldehyde production rate of the zinc, oxygen double vacancy titania / cadmium zinc sulfide heterojunction hollow microspheres of the present application is the highest, which can reach 323.5 μmol g -1 h -1 . While the benzaldehyde production rates of the anatase titania hollow microspheres, the oxygen vacancy containing titania hollow microspheres and the cadmium zinc sulfide nanoparticles are 9.5, 19.1 and 77.4 μmol g -1 h -1 .

[0134] It can be seen that the zinc, oxygen double vacancy titania / cadmium zinc sulfide heterojunction hollow microspheres have the most excellent photocatalytic oxidation activity. As shown in Figure 9 b, all the samples show benzaldehyde product selectivity of more than 97%, and the zinc, oxygen double vacancy titania / cadmium zinc sulfide heterojunction hollow microspheres show benzaldehyde product selectivity of 99%, and no other by-products are detected. As shown in Figure 9 c, the main product of photocatalytic reduction of carbon dioxide is carbon monoxide. The carbon monoxide production rate of the titania hollow microspheres is only 8.4 μmol g -1 h -1 , which is lower than that of the oxygen vacancy containing titania hollow microspheres (17.4 μmol g -1 h -1 ).

[0135] Therefore, the increase in the carbon monoxide production rate is attributed to the positive role of oxygen vacancies in improving light capture ability, photogenerated carrier separation efficiency and carbon dioxide activation. However, these improvements are not sufficient to fundamentally improve the photocatalytic performance of titania. The carbon monoxide production rate of the zinc, oxygen double vacancy titania / cadmium zinc sulfide heterojunction hollow microspheres is as high as 105 μmol g -1 h -1 , which is 6.0 and 13.8 times that of the oxygen vacancy containing titania hollow microspheres and the cadmium zinc sulfide (7.6 μmol g -1 h -1 ), respectively.

[0136] Obviously, the strategy of constructing double vacancy Z-heterojunction successfully improves the performance of photocatalytic reduction of carbon dioxide. As can be seen from formulas (1) and (2), the main products of photocatalytic reduction are carbon monoxide and hydrogen. The production of hydrogen is because the protons produced by oxidation of benzyl alcohol are reduced to hydrogen when they obtain photogenerated electrons.

[0137] As shown in Figure 9 d, the hydrogen production rate of the zinc, oxygen double vacancy titania / cadmium zinc sulfide heterojunction hollow microspheres is the highest, which is 205 μmol g -1 h -1The amount of photocatalytic reduction products (total production rate of carbon monoxide and hydrogen is 310 μmol g) - 1 h -1 The amount of oxidation products (benzaldehyde production rate is 323.5 μmol g) and the amount of oxidation products (benzaldehyde production rate is 323.5 μmol g) -1 h -1 The numbers are almost equal. The underlying reason is that the number of photogenerated holes used for photocatalytic oxidation in this system is equal to the number of photogenerated electrons consumed.

[0138] This invention also tested the photocatalytic cycling stability of the titanium dioxide / cadmium sulfide zinc heterojunction hollow microspheres, such as... Figure 10 As shown.

[0139] from Figure 10 The hollow microspheres with zinc-oxygen dual-vacancy titanium dioxide / zinc cadmium sulfide heterojunctions exhibited essentially unchanged photocatalytic activity after five cycles, demonstrating their excellent stability. This superior cycling stability is attributed to the construction of the titanium dioxide / zinc cadmium sulfide Z-type heterojunction. Due to the unique photogenerated carrier transfer mechanism of the Z-type heterojunction, the photocatalytic oxidation reaction occurs on the chemically stable titanium dioxide surface, while the photocatalytic reduction reaction primarily occurs on the zinc cadmium sulfide surface. This avoids the oxidation of zinc cadmium sulfide by photogenerated holes and the resulting photocorrosion.

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a catalyst of titanium dioxide / zinc cadmium sulfide heterojunction hollow microspheres with zinc and oxygen dual vacancies, characterized in that, Prepared by the following steps: Step (1): Synthesize hollow titanium dioxide microspheres; Step (2): Titanium dioxide / zinc cadmium sulfide heterojunction hollow microspheres are prepared by using the titanium dioxide hollow microspheres obtained in step (1); The titanium dioxide / cadmium sulfide zinc heterojunction hollow microspheres include a substrate of titanium dioxide hollow microspheres containing oxygen vacancies and zinc sulfide zinc nanoparticles containing zinc vacancies grown on the surface of titanium dioxide hollow microspheres, thereby forming titanium dioxide / cadmium sulfide zinc heterojunction hollow microspheres with zinc and oxygen double vacancies. The specific steps (1) are as follows: Step (1.1): SiO2 microspheres were prepared by the Stober method using tetraethyl orthosilicate and concentrated ammonia as the main raw materials; Step (1.2): Using the SiO2 microspheres obtained in step (1.1), concentrated ammonia, and tetrabutyl titanate as the main raw materials, amorphous titanium dioxide film coated with silica core-shell microspheres is obtained by sol-gel combined with heat treatment method. Step (1.3): The amorphous titanium dioxide film obtained in step (1.2) is coated with silica core-shell microspheres and heated to obtain anatase phase titanium dioxide film coated with silica core-shell microspheres; Step (1.4): The anatase phase titanium dioxide film obtained in step (1.3) is coated with silica core-shell microspheres to obtain etched microspheres by sodium hydroxide etching. Step (2) specifically involves using the etched microspheres obtained in step (1), zinc nitrate hexahydrate, cadmium nitrate hexahydrate, and L-cysteine ​​as the main raw materials to obtain titanium dioxide / zinc sulfide Z-type heterojunction hollow microspheres with zinc and oxygen double vacancies through an in-situ hydrothermal method.

2. The method for preparing the catalyst of titanium dioxide / zinc cadmium sulfide heterojunction hollow microspheres with zinc and oxygen double vacancies according to claim 1, characterized in that: The titanium dioxide / cadmium sulfide zinc heterostructure hollow microspheres are oxygen-vacancy-containing TiO2 hollow microspheres loaded with Zn containing Zn vacancies. 0.28 Cd 0.72 S.

3. The method for preparing the catalyst of titanium dioxide / zinc cadmium sulfide heterojunction hollow microspheres with zinc and oxygen double vacancies according to claim 2, characterized in that: The average particle size of the zinc cadmium sulfide nanoparticles is 20nm-30nm.

4. The method for preparing the catalyst of titanium dioxide / zinc cadmium sulfide heterojunction hollow microspheres with zinc and oxygen double vacancies according to claim 1, characterized in that: Specifically, step (1.1) involves mixing 8 ml-12 ml of tetraethyl orthosilicate (TEOS) and 80 ml-120 ml of anhydrous ethanol to obtain solution A, and mixing 50 ml-60 ml of deionized water, 80 ml-120 ml of anhydrous ethanol, and 15 ml-20 ml of concentrated ammonia solution with a concentration of 22 wt%-28 wt% to obtain solution B. Solution B is then added to solution A at room temperature and reacted for 10 h-15 h. After the reaction is completed, the solid is separated by centrifugation and washed alternately with deionized water and anhydrous ethanol, and then dried to obtain SiO2 microspheres. Specifically, step (1.2) involves ultrasonically dispersing 0.2g-0.6g of SiO2 microspheres obtained in step (1.1) in 1ml-3ml of 22wt%-28wt% concentrated ammonia and 200ml-300ml of anhydrous ethanol to obtain solution C; mixing 50ml-100ml of anhydrous ethanol and 2ml-4ml of tetrabutyl titanate to obtain solution D; then adding solution D to solution C and reacting at 58℃-65℃ for 2h-6h; after the reaction is completed, centrifuging is performed, and the solid is washed alternately with deionized water and anhydrous ethanol and dried to obtain amorphous titanium dioxide film-coated silica core-shell microspheres. Specifically, step (1.3) involves coating silica core-shell microspheres with the amorphous titanium dioxide film obtained in step (1.2), heating the temperature to 500℃-600℃ at a rate of 1℃ / min-5℃ / min, holding the temperature for 1h-3h, and then cooling it to room temperature to obtain anatase phase titanium dioxide film coated silica core-shell microspheres. Specifically, step (1.4) involves ultrasonically dispersing the anatase phase titanium dioxide film-coated silica core-shell microspheres obtained in step (1.3) in 50 ml-100 ml of 0.05 M-0.2 M sodium hydroxide solution, reacting at 85 °C-95 °C for 2 h-6 h, centrifuging after the reaction, washing the solid with deionized water, and drying to obtain etched microspheres. Step (2) specifically involves ultrasonically dispersing all the etched microspheres obtained in step (1), 0.4 mmol-0.8 mmol zinc nitrate hexahydrate, 1.0 mmol-2.0 mmol cadmium nitrate hexahydrate, and 3.0 mmol-6.0 mmol L-cysteine ​​in 50 ml-100 ml of deionized water to obtain a dispersion. Then, the dispersion is stirred for 0.5 h-2 h. After stirring, the dispersion is placed in a high-pressure reactor, heated to 180 °C-230 °C, and kept at that temperature for 15 h-20 h. Then, it is cooled to room temperature, and the solid is separated. The solid is washed alternately with deionized water and anhydrous ethanol and dried to obtain titanium dioxide / cadmium sulfide zinc heterojunction hollow microspheres.

5. The method for preparing the catalyst of titanium dioxide / zinc cadmium sulfide heterojunction hollow microspheres with zinc and oxygen double vacancies according to claim 4, characterized in that: Specifically, step (1.1) involves mixing 10 ml of tetraethyl orthosilicate (TEOS) and 100 ml of anhydrous ethanol to obtain solution A, mixing 55 ml of deionized water, 100 ml of anhydrous ethanol, and 18 ml of 28 wt% concentrated ammonia to obtain solution B, adding solution B to solution A at room temperature and reacting for 12 h, centrifuging after the reaction, washing the solid alternately with deionized water and anhydrous ethanol, and drying to obtain SiO2 microspheres; Specifically, step (1.2) involves ultrasonically dispersing 0.5g of SiO2 microspheres obtained in step (1.1) in 2ml of 28wt% concentrated ammonia and 250ml of anhydrous ethanol to obtain solution C; mixing 80ml of anhydrous ethanol and 3.4ml of tetrabutyl titanate to obtain solution D; then adding solution D to solution C and reacting at 60℃ for 4h; after the reaction is completed, centrifuging is performed, and the solid is washed alternately with deionized water and anhydrous ethanol and dried to obtain amorphous titanium dioxide film-coated silica core-shell microspheres; Specifically, step (1.3) involves coating silica core-shell microspheres with the amorphous titanium dioxide film obtained in step (1.2), heating the temperature to 550°C at a rate of 3°C / min, holding the temperature for 2 hours, and then cooling the temperature to room temperature to obtain anatase phase titanium dioxide film coated silica core-shell microspheres. Specifically, step (1.4) involves ultrasonically dispersing the anatase phase titanium dioxide film-coated silica core-shell microspheres obtained in step (1.3) in 80 ml of 0.1 M sodium hydroxide solution, reacting at 90 °C for 4 h, centrifuging after the reaction, washing the solid with deionized water, and drying to obtain etched microspheres. Step (2) specifically involves ultrasonically dispersing all the etched microspheres obtained in step (1), 0.6 mmol zinc nitrate hexahydrate, 1.4 mmol cadmium nitrate hexahydrate, and 4.0 mmol L-cysteine ​​in 60 ml of deionized water to obtain a dispersion. The dispersion is then stirred for 1 h. After stirring, the dispersion is placed in a high-pressure reactor, heated to 200 °C, kept at that temperature for 18 h, and then cooled to room temperature. The solid is then separated, and the solid is washed alternately with deionized water and anhydrous ethanol. The solid is then dried to obtain titanium dioxide / cadmium sulfide zinc heterojunction hollow microspheres.

6. The application of a catalyst with zinc and oxygen dual-vacancy titanium dioxide / zinc cadmium sulfide heterojunction hollow microspheres as a photocatalyst in solar energy conversion, characterized in that: The titanium dioxide / cadmium sulfide zinc heterojunction hollow microspheres are prepared by the catalyst preparation method of titanium dioxide / cadmium sulfide zinc heterojunction hollow microspheres with zinc and oxygen double vacancies as described in any one of claims 1-5. The catalyst catalyzes the carbon dioxide reduction reaction; or The catalyst catalyzes the selective oxidation of benzyl alcohol.

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