Ternary composite catalyst ZnSn (OH) 6 / SrTiO3 / TiO2 as well as preparation method and application thereof in toluene degradation

Abstract

The invention belongs to the technical field of catalysts and preparation thereof, and relates to a ternary composite catalyst ZnSn (OH) 6 / SrTiO3 / TiO2 and a preparation method and application thereof in toluene degradation, the preparation method comprises the following steps: S1, preparing a zinc hydroxystannate precursor solution; s2, preparing SrTiO3 / TiO2 (strontium titanate / titanium dioxide); and S3, preparing the ternary composite catalyst ZnSn (OH) 6 / SrTiO3 / TiO2. The ternary composite catalyst is formed through a hydrothermal method, pyrolysis and coprecipitation, the stability is good, the photoresponse range of the material is widened, carrier separation is further promoted, the photocatalytic activity is improved, and the toluene degradation effect is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalysts and preparation thereof, and relates to a ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 and a preparation method thereof, and application thereof in degrading toluene. Background Art

[0002] Due to its neurotoxicity and environmental mobility, the volatile organic pollutant toluene urgently requires the development of efficient treatment technologies. Its physicochemical properties (such as low boiling point, high volatility, and low flash point) determine its complex environmental migration behavior and multiple hazards. In environmental media, toluene exists primarily in two forms: volatile gas and dissolved liquid. Volatile toluene enters the atmosphere through leakage during production, storage, transportation, and use, becoming a significant source of volatile organic compounds (VOCs). This not only directly pollutes the air but also participates in photochemical reactions to generate secondary pollutants. Dissolved toluene, on the other hand, penetrates into soil and water bodies through industrial wastewater discharge and accidental leaks, disrupting the structure of terrestrial ecosystems and the stability of aquatic communities. Long-term exposure to toluene-contaminated environments can lead to health problems such as respiratory irritation and neurological damage. Its multi-media migration characteristics make pollution control challenging due to the complex cross-media contamination. A comprehensive technology system encompassing source control, process monitoring, and end-of-pipe treatment is urgently needed to reduce its environmental and health risks.

[0003] A diversified system has been developed for the treatment of toluene in industrial waste gas, mainly including physical adsorption, chemical oxidation, bio-enzymatic hydrolysis, photocatalysis, and membrane separation. Among them, semiconductor photocatalytic technology has become a research hotspot due to its green and environmentally friendly characteristics. Its mechanism of action can be summarized as follows: the material is excited by light to produce electron-hole pairs, which are separated on the surface and then participate in oxidation reactions to generate hydroxyl radicals (·OH) and superoxide radicals (·O 2- ) and other strong oxidants, mineralizing toluene into CO2 and H2O through reaction pathways such as electrophilic addition. Highly efficient photocatalytic systems require the construction of a multi-level pore structure to enhance the exposure of active sites and enhance material stability through crystal surface manipulation and heterojunction design.

[0004] As a perovskite material, the new bimetallic hydroxyl compound ZnSn(OH)6 has attracted attention due to its potential in the degradation of organic pollutants, but its research on the photocatalytic degradation of toluene is still significantly insufficient. This is because the large band gap width of the material (about 3.2eV) leads to its limited visible light response ability, which seriously restricts the improvement of light energy utilization efficiency and catalytic performance. Although photocatalysts can usually be modified by various technical means such as heterogeneous structure construction, surface functionalization, and co-catalyst loading, there is still a lack of systematic modification research on the ZnSn(OH)6 system. In particular, how to achieve significant performance improvement through multi-dimensional coordinated regulation is still a technical bottleneck that needs to be broken through in this field. Although the existing modification methods can reduce the band gap of ZnSn(OH)6 by doping with metals (such as Fe, Cu) or non-metals (N, S), it is easy to cause lattice distortion and the dopant is easy to fall off, resulting in poor stability of the modified photocatalyst and affecting the degradation effect; although a single heterojunction can improve the separation of photogenerated carriers, the band matching is still low and the interfacial charge transfer efficiency is limited, which makes the ultraviolet light response of the modified ZnSn(OH)6 poorly matched with the solar spectrum, limiting the light response range of the material. It can be seen that the existing modification methods have poor stability due to weak interactions between materials, making it difficult to achieve a stable synergistic effect, which limits the light response range of the material, resulting in low photocatalytic activity and unsatisfactory degradation effect. Summary of the Invention

[0005] In response to the technical problems of poor stability of photocatalysts and limited light response range of materials in the above-mentioned background technology, the present invention provides a ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 and its preparation method and application in the degradation of toluene.

[0006] The present invention achieves a tight compound of SrTiO3 and TiO2 through a hydrothermal method and thermal decomposition, and then utilizes SrTiO3 / TiO2 to co-modify ZnSn(OH)6 to construct an "electron-hole transport chain" dual-channel mechanism. TiO2 shortens the carrier migration path, while SrTiO3 constructs a hole-rich area through surface oxygen vacancies. The formed ternary composite catalyst not only has good stability, but also broadens the light response range of the material, further promotes carrier separation, thereby enhancing photocatalytic activity and improving the degradation effect of toluene.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A method for preparing a ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 comprises the following steps:

[0009] S1. Preparation of zinc hydroxystannate precursor solution

[0010] Zinc nitrate hexahydrate and stannous chloride pentahydrate are dissolved in water, and then the pH is adjusted to alkaline to obtain a zinc stannate hydroxide precursor solution; in every 40 mL of water, the mass of both zinc nitrate hexahydrate and stannous chloride pentahydrate is (3.5 - 3.7) g;

[0011] S2. Preparation of SrTiO3 / TiO2

[0012] Tetrabutyl titanate, isopropanol and strontium nitrate tetrahydrate are dissolved in water, and then SrTiO3 / TiO2 is synthesized by hydrothermal method and pyrolysis; in every 20 - 25 mL of water, the dosage ratio of tetrabutyl titanate, absolute ethanol, and strontium nitrate tetrahydrate is (2.5 - 3) mL : (25 - 30) mL : (0.65 - 0.85) g;

[0013] S3. Preparation of ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2

[0014] The SrTiO3 / TiO2 obtained in step S2 is added to the zinc stannate hydroxide precursor solution in step S1, and after aging, drying, washing and calcination, the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 is prepared; in every (75 - 80) mL of zinc stannate hydroxide precursor solution, the added mass of the SrTiO3 / TiO2 is (0.8 - 0.9) g.

[0015] Further defined, in step S1, an alkaline solution is used to adjust the pH = 9 ± 0.5, and the alkaline solution is prepared from sodium carbonate, sodium hydroxide and water according to the mass ratio (1.0 - 1.2) : (0.4 - 0.6) : (40 - 60).

[0016] Further defined, the specific process of preparing strontium titanate / titanium dioxide SrTiO3 / TiO2 in step S2 is as follows:

[0017] S2.1. Tetrabutyl titanate is slowly added dropwise to isopropanol and stirred evenly to obtain solution A;

[0018] S2.2. Strontium nitrate tetrahydrate is dissolved in water and stirred evenly to obtain solution B;

[0019] S2.3. Solution B is added dropwise to solution A and mixed evenly to form a mixed system, and then the pH of the mixed system is adjusted to alkaline with an alkali solution to obtain a mixed solution;

[0020] S2.4. The mixed solution is placed in a high-pressure reaction kettle for hydrothermal reaction; then after cooling, washing and drying, a precursor powder is obtained;

[0021] S2.5. The precursor powder is annealed to complete pyrolysis; then washed to neutral and dried to obtain SrTiO3 / TiO2.

[0022] It is further defined that in step S2.3, the alkaline solution is formed by dissolving sodium carbonate and sodium hydroxide in water, and the concentration is 0.05 g / mL.

[0023] It is further defined that in step S2.4, the temperature of the hydrothermal reaction is 100°C to 200°C, and the time of the hydrothermal reaction is 12 hours to 24 hours; the temperature of the drying is 60°C to 80°C, and the time of the drying is 10 hours to 12 hours.

[0024] It is further defined that in step S2.5, the pyrolysis temperature is 350°C to 400°C, the pyrolysis time is 2h to 4h, and the heating rate is 5°C / min to 10°C / min.

[0025] It is further defined that in step S3, the aging time is 6h to 8h, the drying temperature is 60°C to 80°C, and the drying time is 10h to 12h; the calcination temperature is 350°C to 400°C, and the calcination time is 2h to 4h.

[0026] The ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 is prepared by the preparation method of the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2.

[0027] It is further defined that the band gap value of the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 is 2.86 eV.

[0028] The ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 is used as a photocatalyst in photocatalytic degradation of toluene.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 prepared by the present invention is based on the perovskite structural characteristics of SrTiO3 and its energy band matching with TiO2. The close compounding of SrTiO3 and TiO2 is achieved through hydrothermal method and thermal decomposition (annealing treatment). In addition, the introduction of SrTiO3 also optimizes the surface micro-nanostructure of the material, forming multi-level pores, which provides a high specific surface area and active sites for the subsequent loading of ZnSn(OH)6. Then, on the SrTiO3 / TiO2 substrate, it is further loaded onto the surface of ZnSn(OH)6 by co-precipitation. The hydroxylated surface of ZnSn(OH)6 forms a strong chemical bond with the SrTiO3 / TiO2 interface, which enhances the stability of the ternary composite material, reduces the band gap to 2.86eV, broadens the light response range of the material, further promotes carrier separation, and enhances photocatalytic activity.

[0031] 2. The experimental study of the present invention found that in the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2, the photogenerated electrons migrate from the conduction band of TiO2 to SrTiO3, and then transfer to the surface reaction site through the hydroxyl interface of ZnSn(OH)6, while the holes are enriched in the valence band of ZnSn(OH)6, forming an efficient space charge separation; hydroxyl radicals (·OH) and superoxide radicals (·O 2- ) is the main active species, among which the surface hydroxyl groups of ZnSn(OH)6 generate ·OH by capturing holes, while the SrTiO3 / TiO2 heterojunction promotes the decomposition to generate ·O 2- , which is more conducive to the mineralization and degradation of toluene.

[0032] 3. Through experiments, the present invention found that the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 had a toluene degradation rate of 99.20% and a mineralization rate of 98.56%. This indicates that the ternary composite catalyst has excellent photocatalytic performance for toluene and can be used as a photocatalyst to enhance toluene degradation.

[0033] 4. The degradation rate of the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 prepared by the present invention remains at about 99.03% after five cycles, which is only reduced by 0.17%, indicating that the ternary composite catalyst has excellent stability.

[0034] 5. The preparation method of the ternary composite catalyst provided by the present invention adopts a co-precipitation method, a hydrothermal method and a synergistic pyrolysis strategy. The preparation method is simple and efficient, and the reaction can be completed under mild conditions. The reagents used are all conventional, readily available, non-toxic and environmentally friendly raw materials, which are easy to achieve industrial preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is the XRD pattern of different catalysts;

[0036] Figure 2 FT-IR images of different catalysts;

[0037] Figure 3 SEM images of different catalysts;

[0038] Figure 4 TEM and EDS images of 15% ZnSn(OH)6 / SrTiO3 / TiO2;

[0039] Figure 5 This is the XPS pattern of 15% ZnSn(OH)6 / SrTiO3 / TiO2;

[0040] Figure 6 UV spectra and band gap diagrams of different catalysts;

[0041] Figure 7 Toluene performance diagrams for different catalysts;

[0042] Figure 8 XRD and FT-IR diagrams after cycling of 15% ZnSn(OH)6 / SrTiO3 / TiO2;

[0043] Figure 9 In-situ online infrared spectra of 15% ZnSn(OH)6 / SrTiO3 / TiO2. Specific implementation manners

[0044] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] The present invention successfully constructs a ternary composite photocatalytic material ZnSn(OH)6 / SrTiO3 / TiO2 through a step-by-step composite strategy, and significantly improves the photocatalytic performance through the synergistic effect of multiple components. As a wide-bandgap semiconductor, TiO2 can extend the light response range of the composite material to the ultraviolet region, form a heterojunction structure with SrTiO3, promote the transfer of photo-generated electrons from ZnSn(OH)6 to the TiO2 / SrTiO3 interface, effectively inhibit the electron-hole recombination, establish a heterojunction transport mechanism through energy band engineering, and improve the reduction reaction activity while retaining the strong oxidation ability of ZnSn(OH)6.

[0046] The present invention provides a preparation method for a ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2, comprising the following steps:

[0047] S1. Prepare a zinc hydroxystannate precursor solution

[0048] Dissolve zinc nitrate hexahydrate and tin chloride pentahydrate in water, and then adjust the pH to alkaline to obtain a zinc hydroxystannate precursor solution; in every 40 mL of water, the mass of both zinc nitrate hexahydrate and tin chloride pentahydrate is (3.5 - 3.7) g.

[0049] In step S1, an alkaline solution is used to adjust the pH = 9 ± 0.5, and the alkaline solution is prepared from sodium carbonate, sodium hydroxide and water according to a mass ratio of (1.0 - 1.2):(0.4 - 0.6):(40 - 60).

[0050] S2. Prepare strontium titanate / titanium dioxide SrTiO3 / TiO2

[0051] Tetrabutyl titanate, isopropyl alcohol, and strontium nitrate tetrahydrate are dissolved in water, and then SrTiO3 / TiO2 is prepared by hydrothermal method and pyrolysis. The amount ratio of tetrabutyl titanate, anhydrous ethanol, and strontium nitrate tetrahydrate used in every 20-25 mL of water is (2.5-3) mL: (25-30) mL: (0.65-0.85) g.

[0052] The process of preparing strontium titanate / titanium dioxide SrTiO3 / TiO2 in step S2 of the present invention is specifically as follows:

[0053] S2.1. Slowly add tetrabutyl titanate dropwise to isopropyl alcohol and stir to obtain solution A.

[0054] S2.2. Dissolve strontium nitrate tetrahydrate in water and stir to obtain solution B;

[0055] S2.3. Add solution B dropwise to solution A and mix evenly to form a mixed system. Then, adjust the pH of the mixed system to alkaline with an alkaline solution to obtain a mixed solution.

[0056] S2.4. Placing the mixed solution in a high-pressure reactor for hydrothermal reaction; then cooling, washing, and drying to obtain a precursor powder;

[0057] S2.5. Anneal the precursor powder to complete thermal decomposition; then wash it to neutrality and dry it to obtain SrTiO3 / TiO2.

[0058] Preferably, in step S2.3, the alkaline solution is formed by dissolving sodium carbonate and sodium hydroxide in water, and the concentration is 0.05 g / mL.

[0059] Preferably, in step S2.4, the temperature of the hydrothermal reaction is 100° C. to 200° C., and the time of the hydrothermal reaction is 12 h to 24 h; the temperature of the drying is 60° C. to 80° C., and the time of the drying is 10 h to 12 h.

[0060] Preferably, in step S2.5, the pyrolysis temperature is 350°C to 400°C, the pyrolysis time is 2h to 4h, and the heating rate is 5°C / min to 10°C / min. Specifically, the precursor powder is transferred to a crucible and annealed in a muffle furnace to complete the pyrolysis.

[0061] S3. Preparation of zinc hydroxystannate / strontium titanate / titanium dioxide ZnSn(OH)6 / SrTiO3 / TiO2

[0062] The SrTiO3 / TiO2 obtained in step S2 is added to the zinc hydroxystannate precursor solution in step S1, and after aging, drying, washing and calcining, a ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 is prepared.

[0063] Preferably, the dosage of SrTiO3 / TiO2 is 0.8 - 0.9 g, and the dosage of the zinc hydroxystannate precursor solution is 75 - 80 mL.

[0064] In step S3, the aging time is 6 - 8 h, the drying temperature is 60°C - 80°C, and the drying time is 10 h - 12 h; the calcination temperature is 350 - 400°C, and the calcination time is 2 h - 4 h.

[0065] The ZnSn(OH)6 / SrTiO3 / TiO2 prepared by the above method has a significantly reduced band gap, significantly improves the visible light capture ability, promotes the separation of carriers, and can be efficiently used for photocatalytic degradation of toluene.

[0066] The following several specific examples are used to further illustrate the catalyst preparation process and performance of the present invention, but the technical solution of the present invention cannot be further limited thereby.

[0067] It should be noted that the autoclave of the present invention is a stainless steel autoclave with a polytetrafluoroethylene lining. Other operating equipment and instruments without special requirements are conventional equipment and instruments in the art, such as stirring and drying instruments.

[0068] All the pharmaceutical reagents used are analytically pure products purchased from the market.

[0069] Example 1

[0070] The preparation method of the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 provided in this example includes the following steps:

[0071] S1. Preparation of zinc hydroxystannate precursor solution

[0072] S1.1. Under stirring conditions, 3.5 g of zinc nitrate hexahydrate and 3.5 g of stannous chloride pentahydrate are completely dissolved in 40 mL of water to obtain solution A;

[0073] S1.2. Under stirring conditions, 1.06 g of sodium carbonate and 0.4 g of sodium hydroxide are dissolved in 40 mL of water to obtain solution B, that is, an alkaline solution.

[0074] S1.3. Under stirring conditions, solution B is added dropwise to solution A and mixed evenly, and the pH is adjusted to 9 to obtain a mixed solution. In this example, the pH of the solution A system is adjusted with solution B to make it alkaline to obtain the zinc hydroxystannate precursor solution.

[0075] S2. Preparation of strontium titanate / titanium dioxide SrTiO3 / TiO2

[0076] S2.1. Under stirring conditions, 5 mL of tetrabutyl titanate is slowly added dropwise to 25 mL of isopropanol to obtain solution A;

[0077] S2.2. Under stirring conditions, dissolve 0.632 g of strontium nitrate tetrahydrate in 25 mL of water to obtain solution B;

[0078] S2.3. Under stirring conditions, slowly add solution B dropwise to solution A and mix evenly to obtain solution D. Then, add solution C (alkali solution) dropwise to solution D and adjust the pH to alkaline (preferably pH = 9) to obtain a mixed solution;

[0079] S2.4. Place the mixed solution in a 100 mL stainless steel autoclave with a PTFE liner and keep it at 180 °C in an oven for 24 h. The generated reactants are cooled, washed, and dried to obtain precursor powder;

[0080] S2.5. Transfer the precursor powder to a crucible and perform annealing treatment in a muffle furnace to complete pyrolysis. Specifically, perform annealing treatment with a programmed heating rate of 5 °C / min to 350 °C in an air atmosphere and keep it at a constant temperature for 2 h. The final product is washed with deionized water until neutral and then dried in a vacuum oven to obtain SrTiO3 / TiO2.

[0081] Preferably, under stirring conditions, dissolve sodium carbonate and sodium hydroxide in water to obtain solution C (alkali solution) with a concentration of 0.05 mg / L.

[0082] S3. Preparation of zinc stannate hydroxide / titanium strontium oxide / titanium dioxide ZnSn(OH)6 / SrTiO3 / TiO2

[0083] Add 0.85 g of SrTiO3 / TiO2 obtained in step S2 to 80 mL of the zinc stannate hydroxide precursor solution in step S1 to finally form a homogeneous and stable sol system. Wash it alternately with deionized water and absolute ethanol three times to remove unreacted ionic species, and finally dry it in a vacuum environment at 80 °C for 8 h to obtain the ternary composite catalyst 15% ZnSn(OH)6 / SrTiO3 / TiO2, where 15% is the mass fraction of ZnSn(OH)6.

[0084] Example 2

[0085] A preparation method of a ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 provided in this example includes the following steps:

[0086] S1. Preparation of zinc stannate hydroxide precursor solution

[0087] This step is the same as that in Example 1.

[0088] S2. Preparation of titanium strontium oxide / titanium dioxide SrTiO3 / TiO2

[0089] This step is the same as that in Example 1.

[0090] S3. Prepare zinc stannate hydroxide / strontium titanate / titanium dioxide ZnSn(OH)6 / SrTiO3 / TiO2

[0091] This step refers to Example 1. The difference from Example 1 is that 0.9 g of SrTiO3 / TiO2 is added to 80 mL of the zinc stannate hydroxide precursor solution in step S1 to obtain a ternary composite catalyst 10% ZnSn(OH)6 / SrTiO3 / TiO2, where 10% is the mass fraction ratio of ZnSn(OH)6.

[0092] Example 3

[0093] A preparation method of a ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 provided in this example includes the following steps:

[0094] S1. Prepare a zinc stannate hydroxide precursor solution

[0095] This step is the same as that in Example 1.

[0096] S2. Prepare strontium titanate / titanium dioxide SrTiO3 / TiO2

[0097] This step is the same as that in Example 1.

[0098] S3. Prepare zinc stannate hydroxide / strontium titanate / titanium dioxide ZnSn(OH)6 / SrTiO3 / TiO2

[0099] This step refers to Example 1. The difference from Example 1 is that 0.8 g of SrTiO3 / TiO2 is added to 80 mL of the zinc stannate hydroxide precursor solution in step S1 to obtain a ternary composite catalyst 20% ZnSn(OH)6 / SrTiO3 / TiO2, where 20% is the mass fraction ratio of ZnSn(OH)6.

[0100] Examples 4 to 8

[0101] The preparation methods of Examples 4 to 8 are the same as that in Example 1, except that the raw material ratios and the reaction parameters used are different. For details, see Table 1.

[0102] Table 1 Preparation parameters of Examples 4 to 8

[0103]

[0104]

[0105] Further explore the performance of the catalyst prepared in the above embodiments. At the same time, in order to illustrate the technical advantages of the photocatalytic material of the present invention, the following comparative examples are added.

[0106] Comparative Example 1: Preparation of ZnSn(OH)6

[0107] S1.1: Under stirring conditions, dissolve 3.5 g of zinc nitrate hexahydrate and 3.5 g of tin chloride pentahydrate completely in 40 mL of water to obtain solution A.

[0108] S1.2: Under stirring conditions, dissolve 1.06 g of sodium carbonate and 0.4 g of sodium hydroxide in 40 mL of water to obtain solution B.

[0109] S1.3: Under stirring conditions, slowly add solution B dropwise to solution A and mix evenly, then adjust the pH to 9. The suspension is aged at room temperature for 6 h. The sample is washed alternately three times with deionized water and absolute ethanol. Finally, the precursor of the sample is placed in a vacuum drying oven and dried at 60 °C for 12 h, and then ground with an agate mortar to obtain white powder of ZnSn(OH)6 with a regular layered structure.

[0110] Comparative Example 2: Preparation of SrTiO3

[0111] S3.1: First, dissolve 2.1 g of strontium nitrate tetrahydrate in 20 mL of ethylene glycol, and stir evenly under a water bath condition of 80 °C to obtain a mixed solution.

[0112] S3.2: Secondly, add 3.5 ml of tetrabutyl titanate dropwise to the system and continuously stir for 2 h to ensure that the solution is mixed evenly.

[0113] S3.3: Slowly add 30 mL of 5 mol / L sodium hydroxide solution to make the pH of the system maintain at 13.5.

[0114] S3.4: Transfer the above mixed solution to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene, and keep it at 180 °C in an oven for 24 h. After the reaction kettle is cooled to room temperature, wash it several times with deionized water and absolute ethanol respectively, and dry the obtained precipitate at 60 °C for 12 h to obtain SrTiO3.

[0115] Comparative Example 3: Preparation of TiO2

[0116] S3.1: First, dissolve 5.0 mL of tetrabutyl titanate in 25 mL of isopropanol, stir for 15 min, and then add 1.0 mL of water dropwise and stir for 30 min to obtain a mixed solution.

[0117] S3.2. Transfer the mixed solution to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and maintain it in an oven at 180°C for 8 h. After the autoclave cools to room temperature, wash it several times with deionized water and anhydrous ethanol, respectively. Dry the resulting precipitate at 60°C for 12 h to obtain a dry sample.

[0118] S3.3. Place the dried sample in a 100 mL crucible, and place the crucible in a muffle furnace. Raise the temperature to 350°C at a heating rate of 5°C / min and maintain for 2 h to obtain TiO2.

[0119] The performance of the ternary composite catalyst prepared by the present invention was studied through the following experimental tests.

[0120] Test 1

[0121] Phase analysis was carried out using a D8-Advance X-ray diffractometer from Bruker, Germany, to characterize the crystal structure of the sample. The experiment analyzed the phase composition of the material through the correspondence between the lattice plane spacing and the diffraction angle.

[0122] Samples: ZnSn(OH)6 prepared in Comparative Example 1, SrTiO3 prepared in Comparative Example 2, TiO2 prepared in Comparative Example 3, / SrTiO3 / TiO2 and 15% ZnSn(OH)6 / SrTiO3 / TiO2 prepared in Example 1, 10% ZnSn(OH)6 / SrTiO3 / TiO2 prepared in Example 2, and 20% ZnSn(OH)6 / SrTiO3 / TiO2 catalysts.

[0123] Experimental process: Continuous scanning mode was used during the test, with scanning angles covering 10° to 80°, and continuous scanning was performed with a step increment of 0.02°. The scanning speed was 8° / min to ensure data acquisition accuracy. In the sample preparation process, the experimental samples were finely ground with an agate mortar, and a standard tablet pressing method was used to prepare a flat test surface, effectively eliminating the influence of orientation effect on diffraction intensity. The XRD patterns of ZnSn(OH)6, SrTiO3, TiO2, SrTiO3 / TiO2, 10% ZnSn(OH)6 / SrTiO3 / TiO2, 15% ZnSn(OH)6 / SrTiO3 / TiO2 and 20% ZnSn(OH)6 / SrTiO3 / TiO2 photocatalysts were obtained, and the results are as follows: Figure 1 shown.

[0124] See also Figure 1SrTiO3 has six characteristic peaks, located at 22.76°, 32.40°, 39.98°, 46.48°, 67.85°, and 77.20°, respectively. These diffraction peaks correspond to the (100), (110), (111), (200), (220), and (310) crystal planes of the standard card PDF#35-0734, confirming its cubic perovskite structure. The main diffraction peaks of pure ZnSn(OH)6 appear at 19.62°, 22.72°, 32.41°, 40.04°, 46.64°, 52.42° and 57.72°, corresponding to the (111), (200), (220), (222), (400), (420) and (422) crystal planes of the perovskite structure, respectively, which are consistent with the crystal characteristics of perovskite-type hydroxystannate (PDF#73-2384). TiO2 has six characteristic peaks, located at 25.22°, 37.81°, 48.01°, 53.92°, 54.93°, and 62.72°, respectively. These diffraction peaks correspond to the (101), (004), (200), (105), (211), and (204) crystal planes of anatase TiO2, corresponding to standard card PDF#21-1272. In the composite material, the characteristic peaks of ZnSn(OH)6, SrTiO3, and TiO2 are clearly visible and no obvious impurity peaks appear, indicating that the crystal structures of the three are preserved during the composite process. It is worth noting that the peak intensity of the ZnSn(OH)6, SrTiO3, and TiO2 crystal planes of the composite material decreases slightly, which may be due to the influence of multiphase interface interaction on the crystallization integrity. In addition, no significant shift was observed in the characteristic peak positions of the three components, indicating that the composite process did not cause obvious lattice distortion. The above results confirmed the successful construction of the ZnSn(OH)6 / SrTiO3 / TiO2 ternary composite catalyst.

[0125] Test 2

[0126] The experiment used the FTS-3000 spectral system of Digilab, a US company, and was tested in a constant temperature and humidity laboratory environment. Functional groups were identified by analyzing the characteristic absorption peaks generated by molecular vibrational energy level transitions.

[0127] Samples: ZnSn(OH)6 prepared in Comparative Example 1, SrTiO3 prepared in Comparative Example 2, TiO2 prepared in Comparative Example 3, / SrTiO3 / TiO2 and 15% ZnSn(OH)6 / SrTiO3 / TiO2 prepared in Example 1, 10% ZnSn(OH)6 / SrTiO3 / TiO2 prepared in Example 2, and 20% ZnSn(OH)6 / SrTiO3 / TiO2 catalysts.

[0128] Experimental process: The sample preparation strictly follows the sample / KBr ratio of 1:100 (m / m). After being fully ground in an agate mortar, it is pressed into a transparent sheet with a diameter of 13 mm under a pressure of 10 MPa. During the test, a blank KBr background spectrum is collected simultaneously, and dynamic background subtraction, baseline correction and Savitzky-Golay smoothing are performed using OMNIC 9.2 software. The FT-IR spectra of ZnSn(OH)6, SrTiO3, TiO2, SrTiO3 / TiO2, 10% ZnSn(OH)6 / SrTiO3 / TiO2, 15% ZnSn(OH)6 / SrTiO3 / TiO2 and 20% ZnSn(OH)6 / SrTiO3 / TiO2 are obtained, as shown in the figure. Figure 2 shown.

[0129] See also Figure 2 The characteristic peak of pure ZnSn(OH)6 is at 3400 cm -1 The peak at 500-700 cm-1 is the broad peak of stretching vibration of hydroxyl (-OH). -1 The absorption peaks in the range are attributed to the vibration modes of Zn-O and Sn-O. In the infrared spectrum of SrTiO3, the characteristic vibration peak of Ti-O bond is located at 600cm -1 Nearby, while TiO2 is at 400-700cm -1 In the composite material, the typical Ti-O stretching vibration peak is at 620cm -1 , 540cm -1 and 598cm -1 The characteristic vibration peaks corresponding to Zn-O, Sn-O and Ti-O respectively maintain the original wavenumber positions and peak shape parameters and are clearly visible, with no new absorption peaks appearing, indicating that no new chemical bonds are formed and the original skeleton structures of the components are destroyed during the ternary composite process.

[0130] Test 3

[0131] In this study, a field emission scanning electron microscope (FESEM) from Zeiss ULTRA plus was used to characterize and analyze the surface morphology of the samples.

[0132] Samples: ZnSn(OH)6 prepared in Comparative Example 1, SrTiO3 prepared in Comparative Example 2, TiO2 prepared in Comparative Example 3, and 15% ZnSn(OH)6 / SrTiO3 / TiO2 catalyst.

[0133] Experimental process: First, the powder sample was ultrasonically dispersed in anhydrous ethanol for 30 minutes to achieve particle deagglomeration. Then, a micropipette was used to accurately drop the suspension onto a conductive silicon substrate (10×10mm) with a polished surface, and the suspension was allowed to stand in a clean drying oven to complete solvent evaporation. The entire test process was completed in a high vacuum chamber, and finally the three-dimensional topological information of the sample surface at the nanoscale was obtained. The SEM images of ZnSn(OH)6, SrTiO3, TiO2, and 15% ZnSn(OH)6 / SrTiO3 / TiO2 photocatalysts were obtained, and the results are as follows: Figure 3 shown

[0134] See also Figure 3 , Figure 3 (a) TiO2 appears as nanoparticles, while Figure 3 (b) SrTiO3 presents cubic particles with smooth surface and no obvious agglomeration. Figure 3 (c) Pure ZnSn(OH)6 presents a regular flake structure with a smooth surface and clear edges, indicating that its crystal growth is anisotropic. Figure 3 (d) shows that the surface of 15% ZnSn(OH)6 / SrTiO3 / TiO2 is significantly roughened, and no independent particles of SrTiO3 or TiO2 are observed, indicating that the three form a uniform composite through heterogeneous structural growth. Furthermore, the introduction of SrTiO3 and TiO2 changes the interfacial energy distribution of the composite system, inhibiting the anisotropic growth of the single phase of ZnSn(OH)6, thereby causing morphological roughening. Therefore, the rough surface and porous structure can provide more active sites, enhance light absorption or catalytic performance, and the close contact of the three phases is conducive to the rapid separation of photogenerated carriers and improve photocatalytic efficiency.

[0135] Test 4

[0136] This study employed advanced transmission electron microscopy (TEM) to systematically characterize the microstructural characteristics of the materials. Using a JEOL JEM-F200 instrument from Japan, ultra-high spatial resolution atomic-scale observations were achieved at an accelerating voltage of 200 kV. High-angle annular dark-field imaging was then employed, leveraging the atomic number contrast effect to clearly visualize the distribution of different elements within the material. Combined with an energy spectrum system for surface scanning analysis, this enabled quantitative characterization of elemental spatial distribution at the submicron scale.

[0137] Sample: 15% ZnSn(OH)6 / SrTiO3 / TiO2 catalyst prepared in Example 1.

[0138] Experimental procedure: A uniformly dispersed nanoparticle suspension was obtained by ultrasonic-assisted ethanol dispersion method. The sample was precisely dropped onto a copper mesh substrate with an ultrathin carbon film using a micropipette, and after vacuum drying, a thin area suitable for high-resolution observation was formed. TEM and EDS images of the 15% ZnSn(OH)6 / SrTiO3 / TiO2 photocatalyst were obtained, and the results are as Figure 4 shown.

[0139] See Figure 4 , and further reveals the fine structural characteristics of the material from TEM analysis Figure 4 (d-f). In the high-resolution image Figure 4 (e), the (101) lattice fringe of anatase TiO2 is 0.35 nm, and the lattice spacing of 0.27 nm corresponds to the (220) crystal plane of ZnSn(OH)6, confirming the successful composite of the two phases. Selected area electron diffraction Figure 4 (f) shows the characteristics of polycrystalline diffraction rings, which is consistent with the conclusion of the coexistence of the two phases in the XRD results. Element distribution mapping Figure 4 (g-j) shows that Ti and O elements are uniformly dispersed on ZnSn(OH)6, which highly coincides with the spatial distribution of Zn and Sn elements. It indicates that no obvious phase separation occurred during the composite process of ZnSn(OH)6. The uniform distribution of Zn, Sn, Ti, and O elements is shown, and no impurities are present. These results indicate that the ZnSn(OH)6 / TiO2 composite material was successfully synthesized.

[0140] Experiment 5

[0141] In this study, a Shimadzu / Kratos AXIS SUPRA+ type high-resolution photoelectron spectroscopy system was used to analyze the components of each chemical state, and finally, a corresponding relationship model between the chemical state of elements and the coordination structure was established.

[0142] Sample: The catalyst of 15% ZnSn(OH)6 / SrTiO3 / TiO2 prepared in Example 1.

[0143] Experimental procedure: To balance the signal-to-noise ratio and energy resolution with an energy of 100 eV, a scanning step of 0.1 eV was used to ensure the accurate analysis of spectral peak characteristics. The charge correction process strictly followed the surface analysis standard. The C1s characteristic peak of the carbon contamination layer adsorbed on the sample surface (binding energy 284.8 eV, corresponding to the C-C / C-H bonding state) was selected as the internal standard for compensation calibration, and ThermoAvantage professional analysis software was used for spectral analysis. XPS images of the 15% ZnSn(OH)6 / SrTiO3 / TiO2 photocatalyst were obtained, and the results are as Figure 5 shown.

[0144] See Figure 5 , asFigure 5 As shown in Figure 5 (a), the XPS full-spectrum analysis shows that the main elements present in the material are Zn, Sn, Sr, Ti, and O, and no obvious impurity peaks are observed, indicating a high purity of the material. The high-resolution Zn 2p spectrum is shown in 3 / 2 and 1 / 2 , and the two peaks at 1021.8 eV and 1044.9 eV correspond to Zn 2p Figure 5 (c), the two peaks at 486.5 eV and 494.9 eV correspond to Sn 3d 5 / 2 and Sn 3d 3 / 2 , respectively, confirming that the Sn element exists in the +4 valence state. In addition, the high-resolution Sr 3d spectrum as shown in Figure 5 (d) shows two peaks at 133.4 eV and 135.2 eV, corresponding to Sr 3d 5 / 2 and Sr 3d 3 / 2 , respectively, indicating that the Sr element exists in the +2 valence state. The high-resolution Ti 2p spectrum as shown in Figure 5 (e) shows peaks at 458.6 eV and 464.3 eV corresponding to Ti 2p 3 / 2 and Ti 2p 1 / 2 , respectively, confirming that the Ti element exists in the +4 valence state. Finally, from Figure 5 (f), the peaks of the high-resolution O 1s spectrum at 529.8 eV and 531.5 eV are attributed to lattice oxygen and surface-adsorbed hydroxyl groups (-OH), respectively. The above results indicate that each element in the ZnSn(OH)6, SrTiO3, and TiO2 composite material exists in the expected chemical valence state, and no obvious impurity phases or chemical bond breakage phenomena are observed, further confirming the structural stability of the composite material. In addition, the presence of the hydroxyl peak in the O 1s spectrum indicates that the material surface has abundant active sites.

[0145] Experiment 6

[0146] As an important means to characterize the optical properties of semiconductor materials, ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) was used in this study to test with a Shimadzu UV-3600Plus double-beam spectrometer.

[0147] Samples: The catalysts of ZnSn(OH)6 prepared in Comparative Example 1, SrTiO3 prepared in Comparative Example 2, TiO2 prepared in Comparative Example 3, / SrTiO3 / TiO2 prepared in Example 1, 15% ZnSn(OH)6 / SrTiO3 / TiO2, 10% ZnSn(OH)6 / SrTiO3 / TiO2 prepared in Example 2, and 20% ZnSn(OH)6 / SrTiO3 / TiO2.

[0148] Experimental process: BaSO4 powder with standard whiteboard characteristics was used as a reference background. The diffuse reflectance spectrum data of the material was acquired by full-band scanning (200-1000nm). During the scanning process, a high-precision data acquisition interval of 2nm was set to ensure the resolution of the spectral characteristics.

[0149] For the quantitative analysis of semiconductor band gap, the functional relationship between photon energy and absorption coefficient is established in combination with the Tauc equation:

[0150] (αhv) 1 / n =A(hv-E g )

[0151] In this model, the exponent n is selected based on the intrinsic electronic transition mechanism of the material: when a direct transition occurs, n = 1 / 2, while an indirect transition process corresponds to n = 2. By fitting the experimental data to different n values in a linear segment and extrapolating the curve tangent to the abscissa intercept, the characteristic band gap value E of the material can be obtained. g The UV and band gap diagrams of ZnSn(OH)6, SrTiO3, TiO2, SrTiO3 / TiO2, 10% ZnSn(OH)6 / SrTiO3 / TiO2, 15% ZnSn(OH)6 / SrTiO3 / TiO2 and 20% ZnSn(OH)6 / SrTiO3 / TiO2 were obtained. The results are shown in Figure 6 shown.

[0152] See also Figure 6 The band gap of the composite material measured by UV-visible absorption spectroscopy is as follows Figure 6 (a) The band gaps of ZnSn(OH)6, SrTiO3, TiO2, 1:1 SrTiO3 / TiO2, and 15% ZnSn(OH)6 / SrTiO3 / TiO2 were found to be 3.28 eV, 3.18 eV, 3.20 eV, 3.07 eV, and 2.86 eV, respectively, based on Tauc plot fitting. The band gap of the composite material dropped to 2.86 eV, broadening the light absorption range. This reduction in the band gap is primarily due to the band coupling effect between ZnSn(OH)6 and SrTiO3 / TiO2, which reduces the energy required for photogenerated electron transitions.

[0153] Test 7

[0154] In this study, a closed reaction system was used to conduct catalytic degradation experiments on gaseous toluene, and a gas chromatograph was used to achieve real-time monitoring of gas components during the reaction.

[0155] Samples: ZnSn(OH)6 prepared in Comparative Example 1, SrTiO3 prepared in Comparative Example 2, TiO2 prepared in Comparative Example 3, / SrTiO3 / TiO2 and 15% ZnSn(OH)6 / SrTiO3 / TiO2 prepared in Example 1, 10% ZnSn(OH)6 / SrTiO3 / TiO2 prepared in Example 2, and 20% ZnSn(OH)6 / SrTiO3 / TiO2 catalysts.

[0156] Experimental process: 0.1g of photocatalyst was evenly dispersed in a quartz culture dish and placed in a 250mL sealed quartz reactor. After the system was sealed, 2μL of liquid toluene was injected and allowed to stand for 1 hour to reach gas-solid adsorption equilibrium. A 0.6μL gas sample was collected using a trace gas injection needle, and the initial concentrations of toluene and carbon dioxide were determined by gas chromatograph. During the experiment, a 300W xenon lamp light source was turned on, and then the gas composition was detected every 15 minutes to continuously monitor the concentration changes of toluene and its degradation product carbon dioxide in the reaction system. The performance analysis diagrams of ZnSn(OH)6, SrTiO3, TiO2, SrTiO3 / TiO2, 10% ZnSn(OH)6 / SrTiO3 / TiO2, 15% ZnSn(OH)6 / SrTiO3 / TiO2 and 20% ZnSn(OH)6 / SrTiO3 / TiO2 were obtained, and the results are shown as follows. Figure 7 shown.

[0157] The formulas for calculating the toluene degradation rate DR (Degradation rate) and mineralization rate MR (Mineralization rate) are as follows:

[0158] DR=(1-C / C0)×100%

[0159] MR = Δ[CO2] / (7×C0)×100%

[0160] In the above formula, C0 represents the initial concentration of toluene; C represents the toluene concentration at a certain moment; Δ[CO2] represents the concentration of carbon dioxide generated by the reaction.

[0161] See also Figure 7 Under simulated sunlight, the ternary composite system showed excellent pollutant degradation efficiency. Figure 7 As shown in (a), when the ZnSn(OH)6 loading is 15%, the system achieves a toluene degradation rate of 99.20% within 90 minutes, which is higher than that of pure SrTiO3 and TiO2. Figure 7 (b) The apparent rate constants of the catalysts are: 10% ZnSn(OH)6 / SrTiO3 / TiO2 0.02501min -1and 0.04355 min for 15% ZnSn(OH)6 / SrTiO3 / TiO2 -1 and 0.011892 min for 20% ZnSn(OH)6 / SrTiO3 / TiO2 -1 , among which the 15% composite sample exhibits the optimal reaction kinetic characteristics. From the mineralization rate Figure 7 (c), it can be seen that while completing the degradation of toluene, it shows excellent mineralization ability, and the toluene mineralization rate reaches 98.56% within 90 min; indicating that the active species such as ·O 2- and ·OH formed at the heterojunction interface can effectively cut off the aromatic ring structure and achieve the deep mineralization of pollutants. Stability test Figure 7 (d) shows that 15% ZnSn(OH)6 / SrTiO3 / TiO2 maintains excellent performance in five consecutive cycles, and the toluene degradation rate always remains at about 99.03%, confirming that the composite material has good cycle stability. The stability of the composite material is due to the effective charge transport channels formed at the heterojunction interface and the inhibitory effect of the composite structure on the recombination of photogenerated carriers.

[0162] Experiment 8

[0163] The test samples are the catalysts before and after the cycle of 15% ZnSn(OH)6 / SrTiO3 / TiO2 prepared in Example 1.

[0164] By performing XRD and FT-IR tests on the photocatalyst before and after the cycle, the structural stability of the material is further illustrated. The XRD and FT-IR diagrams of 15% ZnSn(OH)6 / SrTiO3 / TiO2 before and after the cycle are obtained, and the results are as Figure 8 shown.

[0165] The study on the structural stability of the 15% ZnSn(OH)6 / SrTiO3 / TiO2 ternary composite catalyst after five toluene degradation cycles shows that its multiphase heterojunction system exhibits excellent synergistic stability. As shown in Figure 8 (a), in the XRD pattern, the intensity and position of the characteristic peaks of the anatase phase of ZnSn(OH)6, SrTiO3 and TiO2 do not show significant shifts after the cycle, and no impurity phase is detected. This indicates that no phase transformation occurs among the three during the repeated catalytic process, and the heterojunction interface structure remains intact. FT-IR spectrum Figure 8 (b) further shows that the peak shape and peak position of the material remain unchanged, proving that the chemical bonding states of the components in the composite system are stable, providing persistent and stable active sites for the catalytic reaction.

[0166] Experiment 9

[0167] In this study, a real-time monitoring system was constructed using the Thermo Fisher Nicoleti S50 in situ diffuse reflectance reaction cell. Time-resolved spectroscopy was used to capture the transient changes of adsorbed species on the catalyst surface, and two-dimensional correlation spectroscopy was combined to reveal the co-evolution of functional group vibration peaks.

[0168] Sample: 15% ZnSn(OH)6 / SrTiO3 / TiO2 catalyst prepared in Example 1.

[0169] Experimental process: In a photocatalytic system simulating a real environment, a visible light-driven system was constructed using a 300W xenon lamp light source coupled with a filter. The reaction gas was precisely controlled by a mass flow controller to form a toluene / dry air mixture (1:50 v / v), with a total flow rate of 30 ml / min, to form a stable adsorption layer on the catalyst surface. By comparing the characteristic peak shifts of the dark adsorption and light degradation processes, the preferential adsorption behavior of toluene molecules on the acid sites can be analyzed, and an in-situ infrared image of 15% ZnSn(OH)6 / SrTiO3 / TiO2 is obtained. The results are as follows: Figure 9 shown.

[0170] See also Figure 9 , at the initial stage of photoexcitation, 1600 cm -1 Benzene ring C=C skeleton vibration and 1450cm -1 The appearance of the characteristic peak of the in-plane bending of methyl CH confirms that toluene molecules form a chemical adsorption layer on the catalyst surface through π-π interaction. As the photocatalytic reaction continues, the peak at 1710 cm -1 Aldehyde C=O and 1380cm -1 The new vibration signal was detected at the carboxylic acid CO, indicating that the adsorbed toluene underwent a gradual oxidation process to generate primary oxidation products such as benzaldehyde and benzoic acid. It is worth noting that at 2345 cm -1 The CO2 asymmetric stretching vibration peak near 3400 cm-1 shows a linear growth trend in intensity. -1 The broadband characteristic peak of hydroxyl radical (·OH) was detected at 3510cm. The two synergistically confirmed the deep mineralization process of organic pollutants. Further analysis found that -1 The characteristic vibration of hydrogen bonded hydroxyl group at 1506cm -1 Ketone C=O, 1742cm -1 The infrared peaks are as follows: the formation and oxidation transformation pathway of benzyl alcohol intermediate is constructed: in ·OH and ·O 2- Under the continuous attack of , benzyl alcohol is dehydrogenated to form benzaldehyde, which is then oxidized to benzoic acid. -1Characteristic absorptions of short-chain organic acids were detected at 1700 cm-1 and 1526 cm-1, revealing the degradation intermediate states of small-molecule carboxylic acids such as oxalic acid and formic acid generated after the cleavage of the aromatic ring. Therefore, the degradation pathway of photocatalytic degradation of toluene by ZnSn(OH)6 / SrTiO3 / TiO2 was obtained: C6H5CH3 → C6H5CH2OH → C6H5CHO → C6H5COOH → HOOC-(CH2) n -COOH → CO2 + H2O, fully presenting the process of pollutant from surface adsorption, step-by-step oxidation to final mineralization.

[0171] The above experimental tests were carried out using the ternary composite catalysts prepared in Examples 1 to 3. When the preparation methods of Examples 4 to 8 were adopted, ternary composite catalysts with similar and close performance to those of Examples 1 to 3 could be obtained. And they were used for the efficient degradation and mineralization of toluene.

[0172] The above are several relatively preferred implementation manners of the preparation method of the present invention. However, it cannot be used as a limitation to the technical solutions protected by the present invention. Any substitution solutions obtained by those of ordinary skill in the art based on the technical idea of the present invention without creative efforts should fall within the protection scope of the present invention.

Claims

1. Preparation method of ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2, characterized in that, It includes the following steps: S1. Prepare a zinc stannate hydroxide precursor solution Dissolve zinc nitrate hexahydrate and tin chloride pentahydrate in water, and then adjust the pH to alkaline to obtain a zinc stannate hydroxide precursor solution; in every 40 mL of water, the mass of both zinc nitrate hexahydrate and tin chloride pentahydrate is (3.5 - 3.7) g; S2. Prepare SrTiO3 / TiO2 Dissolve tetrabutyl titanate, isopropanol, and strontium nitrate tetrahydrate in water, and then synthesize SrTiO3 / TiO2 through hydrothermal method and pyrolysis; in every (20 - 25) mL of water, the dosage ratio of tetrabutyl titanate, absolute ethanol, and strontium nitrate tetrahydrate is (2.5 - 3) mL : (25 - 30) mL : (0.65 - 0.85) g; S3. Prepare the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 Add the SrTiO3 / TiO2 obtained in step S2 to the zinc stannate hydroxide precursor solution in step S1, and prepare the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 after aging, drying, washing, and calcination; in every (75 - 80) mL of zinc stannate hydroxide precursor solution, the added mass of the SrTiO3 / TiO2 is (0.8 - 0.9) g.

2. The preparation method of the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 according to claim 1, characterized in that, In step S1, an alkaline solution is used to adjust the pH = 9 ± 0.5, and the alkaline solution is prepared from sodium carbonate, sodium hydroxide, and water according to the mass ratio (1.0 - 1.2) : (0.4 - 0.6) : (40 - 60).

3. The preparation method of the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 according to claim 1, characterized in that, The specific process of preparing strontium titanate / titanium dioxide SrTiO3 / TiO2 in step S2 is as follows: S2.

1. Slowly drop tetrabutyl titanate into isopropanol and stir evenly to obtain solution A; S2.

2. Dissolve strontium nitrate tetrahydrate in water and stir evenly to obtain solution B; S2.

3. Drop solution B into solution A drop by drop and mix evenly to form a mixed system, and then use an alkali solution to adjust the pH of the mixed system to alkaline to obtain a mixed solution; S2.

4. Place the mixed solution in a high-pressure reactor for hydrothermal reaction; then cool, wash, and dry to obtain a precursor powder; S2.

5. Perform annealing treatment on the precursor powder to complete pyrolysis; Then wash until neutral and dry to obtain SrTiO3 / TiO2.

4. The preparation method of the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 according to claim 3, characterized in that, In step S2.3, the alkali solution is formed by dissolving sodium carbonate and sodium hydroxide in water, and the concentration is 0.05 g / mL.

5. The preparation method of the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 according to claim 3, characterized in that, In step S2.4, the temperature of the hydrothermal reaction is 100℃ - 200℃, the time of the hydrothermal reaction is 12 h - 24 h; the temperature of drying is 60℃ - 80℃, and the time of drying is 10 h - 12 h.

6. The preparation method of the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 according to claim 3, characterized in that, In step S2.5, the temperature of pyrolysis is 350℃ - 400℃, the time of pyrolysis is 2 h - 4 h, and the heating rate is 5℃ / min - 10℃ / min.

7. The preparation method of the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 according to claim 1, characterized in that, In step S3, the aging time is 6 h - 8 h, the drying temperature is 60℃ - 80℃, and the drying time is 10 h - 12 h; the calcination temperature is 350℃ - 400℃, and the calcination time is 2 h - 4 h. The ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 prepared by the preparation method of the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 as described in claim 1.

9. The ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 according to claim 8, characterized in that, The band gap value of the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 is 2.86 eV.

10. The application of the ternary composite catalyst ZnSn(OH)6 / SrTiO3 / TiO2 as described in claim 9 as a photocatalyst in the photocatalytic degradation of toluene.

Images