Preparation method for in-situ etching growth nested SrTiO3 / TiO2 heterojunction photocatalytic material

Abstract

The invention relates to the field of material preparation, in particular to a preparation method for in-situ etching growth of a nested SrTiO3 / TiO2 heterojunction photocatalytic material, and solves the problem that in-situ synthesis of a nested SrTiO3 / TiO2 heterostructure cannot be realized by an existing preparation method. The preparation method specifically comprises the following steps: mixing an aqueous solution of SrCl2. 6H2O with an aqueous solution of LiOH.H2O, stirring to obtain a solution A, adding TiCl4 into a solution of 1, 2-propylene glycol, and stirring to obtain a solution B; mixing and stirring the solution A and the solution B, and carrying out hydrothermal reaction for a period of time to obtain octadecahedron-shaped SrTiO3; after hydrochloric acid hydrothermal etching, the interior of the SrTiO3 is partially etched, and small conical particles grow on the (001) crystal face of the SrTiO3, so that an SrTiO3 and TiO2 internal and external nested structure is formed; and cooling, centrifuging, cleaning and drying to obtain the in-situ etching growth nested SrTiO3 / TiO2 heterojunction photocatalytic material. The preparation method can be carried out under a common hydrothermal condition, is simple to operate and low in cost, has relatively high yield and purity and relatively high photocatalytic activity, and has practical application potential.

Description

Technical Field

[0001] This invention relates to the field of materials preparation, specifically to a method for preparing a nested SrTiO3 / TiO2 heterojunction photocatalytic material by in-situ etching and growth. Background Technology

[0002] SrTiO3, as a typical photocatalytic material, possesses excellent chemical stability, flexible controllability, and thermodynamic properties suitable for photocatalytic reactions, making it promising for applications in energy conversion and environmental purification. However, SrTiO3 monomers have certain limitations: severe recombination of photogenerated electrons and holes makes it difficult for them to migrate to the material surface for redox reactions, which seriously restricts its industrial application.

[0003] Heterojunctions are an important method for improving photocatalytic performance. The work function differences between different components in a heterojunction induce band bending, forming a built-in electric field between different interfaces. This electric field effectively promotes the spatial separation of photogenerated electrons and holes, significantly reducing recombination probability. Furthermore, good interfacial contact reduces charge transfer resistance, further improving carrier transport efficiency. In summary, the thinner SrTiO3 shell in the in-situ etched nested SrTiO3 / TiO2 heterojunction reduces recombination of photogenerated carriers in the bulk phase, facilitating the migration of more carriers to the surface to participate in the reaction.

[0004] In the construction of SrTiO3 / TiO2 heterostructures, Chinese patent CN117504892B synthesized a La / Fe co-doped SrTiO3 / TiO2 composite material. This patent emphasizes the influence of doping on performance, and the preparation process is based on the conversion of TiO2 into a SrTiO3 / TiO2 heterostructure. The resulting SrTiO3 has no specific crystal facets exposed, which is different from the preparation process and structure of this patent. Chinese patent CN117619374B synthesizes a metal-doped SrTiO3 / TiO2, and the claims emphasize the application of this material in the treatment of nitrate wastewater. The SrTiO3 / TiO2 material is prepared by subsequently growing TiO2 on the basis of SrTiO3, and the preparation process uses an organic Ti source, which is completely different from the structure, preparation process and application scenario emphasized by this patent. Reference 1 [J. Mater. Sci. Technol., 2026, 261, [184-191] TiO2 grown on the SrTiO3(001) surface varies in size and has an irregular shape. It only improves the charge separation efficiency by reducing the potential barrier height of the (001) plane, and does not actually form a heterojunction. Reference 2 [Chem.Eng. J., 2025, 517, 160059] grows ultrathin TiO2 layers on all surfaces of SrTiO3 without selective growth. At the same time, TiO2 acts as a surface manipulation layer rather than a heterojunction, and improves the charge separation efficiency by reducing the Schottky barrier on the SrTiO3 surface. Reference 3 [Angew.Chem. Int. Ed. 2019, 58, 1422–1426] prepares SrTiO3 / TiO2 as a multi-shell structure without crystal anisotropy, and the structure is completely different from the structure prepared in this invention.

[0005] To date, no method for preparing in-situ etched growth of nested SrTiO3 / TiO2 heterojunction photocatalytic materials has been found in the literature or published patents. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a nested SrTiO3 / TiO2 heterojunction photocatalytic material by in-situ etching growth.

[0007] The technical solution of this invention is:

[0008] A method for preparing a nested SrTiO3 / TiO2 heterojunction photocatalytic material by in-situ etching growth. Specifically, an aqueous solution of SrCl2·6H2O and an aqueous solution of LiOH·H2O are mixed and stirred to obtain solution A. TiCl4 is added to a solution of 1,2-propanediol and stirred to obtain solution B. Solutions A and B are mixed and stirred and subjected to hydrothermal reaction for a period of time to obtain octahedral SrTiO3. After hydrothermal etching with hydrochloric acid, conical small particles are grown on the (001) crystal face of SrTiO3. As the etching time increases, the size of TiO2 particles gradually increases and is exposed from the (001) crystal face. After cooling, centrifugation, cleaning and drying, the nested SrTiO3 / TiO2 heterojunction photocatalytic material by in-situ etching growth is obtained.

[0009] The method for preparing an in-situ etched growth nested SrTiO3 / TiO2 heterojunction photocatalytic material is characterized by using SrCl2·6H2O and TiCl4 as Sr source and Ti source, respectively; and using LiOH·H2O and 1,2-propanediol as crystal face growth control agents.

[0010] The method for preparing an in-situ etched growth nested SrTiO3 / TiO2 heterojunction photocatalytic material is characterized by: dissolving 0.5~1.2 g SrCl2·6H2O in 10~24 mL of deionized water, and dissolving 4~8 g LiOH·H2O in 30~60 mL of deionized water to obtain solution A; and adding 0.26~0.52 mL TiCl4 to 25~50 mL of deionized water containing 2~4 g 1,2-propanediol in an ice-water bath.

[0011] The method for preparing an in-situ etched growth nested SrTiO3 / TiO2 heterojunction photocatalytic material is characterized by: mixing and stirring solution A and solution B for 30 min, then hydrothermally reacting at 180~200 ℃ for 12~36 h, and drying and collecting to obtain SrTiO3 with exposed (001) and (110) crystal planes.

[0012] The method for preparing an in-situ etched growth nested SrTiO3 / TiO2 heterojunction photocatalytic material is characterized by growing TiO2 on the SrTiO3(001) crystal plane by hydrothermal etching with hydrochloric acid at a concentration of 0.01~0.05 M.

[0013] The method for preparing an in-situ etched growth nested SrTiO3 / TiO2 heterojunction photocatalytic material is characterized by: dissolving 200~400 mg SrTiO3 in 50 mL of hydrochloric acid solution of a specific concentration, and reacting under hydrothermal conditions at 180~220 ℃ for 12~36 h.

[0014] The design concept of this invention is as follows:

[0015] Based on the special requirements of photocatalysts for charge separation and migration, the design concept of this invention is to obtain nested SrTiO3 / TiO2 heterojunction photocatalytic materials through simple in-situ etching experiments using readily available and low-cost raw materials.

[0016] The advantages and beneficial effects of this invention are as follows:

[0017] 1. The hydrothermal method used in this invention is relatively simple and the conditions are mild. The in-situ etched nested SrTiO3 / TiO2 heterojunction photocatalyst has good photocatalytic water splitting performance and has the potential for practical application.

[0018] 2. The in-situ growth method used in this invention forms a tight interfacial connection at the atomic scale between SrTiO3 and TiO2, which is beneficial for charge separation and transfer. The construction of the heterojunction provides a stronger driving force for the transfer of photogenerated electrons and holes, reduces the recombination of photogenerated carriers in the bulk phase, and facilitates the migration of more carriers to the surface to participate in the reaction. Attached Figure Description

[0019] Figure 1 Solution A, obtained by mixing an aqueous solution of SrCl2·6H2O with an aqueous solution of LiOH·H2O, was mixed with TiCl4 in a 1,2-propanediol solution to obtain solution B. The mixture was stirred and hydrothermally reacted for a period of time to obtain SrTiO3. Then, a series of nested SrTiO3 / TiO2 heterojunction morphologies were obtained by hydrothermal etching with hydrochloric acid for different times.

[0020] Figure 2 Solution A, obtained by mixing an aqueous solution of SrCl2·6H2O with an aqueous solution of LiOH·H2O, is mixed with TiCl4 in a 1,2-propanediol solution to obtain solution B. The mixture is stirred and subjected to hydrothermal reaction for a period of time to obtain SrTiO3. Then, nested SrTiO3 / TiO2 is obtained by hydrothermal etching with hydrochloric acid for 36 h. Finally, Au and MnO are photodeposited as co-catalysts. x The location allows observation of the migration direction of photogenerated electrons and holes, thus revealing the effect of charge space separation.

[0021] Figure 3 Solution A, obtained by mixing an aqueous solution of SrCl2·6H2O with an aqueous solution of LiOH·H2O, was mixed with TiCl4 in a 1,2-propanediol solution to obtain solution B. The mixture was stirred and subjected to hydrothermal reaction for a period of time to obtain SrTiO3. Raman patterns of a series of nested SrTiO3 / TiO2 heterojunctions were then obtained by hydrothermal etching with hydrochloric acid for different times. The horizontal axis represents the diffraction angle Raman shift (cm). -1The vertical axis, intensity, represents the intensity (Counts).

[0022] Figure 4 The elemental distribution of the nested SrTiO3 / TiO2 heterojunction was obtained by mixing solution A, which was obtained by mixing aqueous solutions of SrCl2·6H2O and LiOH·H2O, and adding TiCl4 to 1,2-propanediol solution to obtain solution B. The mixture was stirred and hydrothermally reacted for a period of time to obtain SrTiO3. Then, the nested SrTiO3 / TiO2 heterojunction was obtained by hydrothermal etching with hydrochloric acid for 36 h.

[0023] Figure 5 Solution A, obtained by mixing an aqueous solution of SrCl2·6H2O with an aqueous solution of LiOH·H2O, was mixed with TiCl4 in a 1,2-propanediol solution to obtain solution B. The mixture was stirred and subjected to hydrothermal reaction for a period of time to obtain SrTiO3. Then, a series of nested SrTiO3 / TiO2 heterojunctions were obtained through hydrothermal etching with hydrochloric acid for different times, demonstrating their photocatalytic water splitting performance. The horizontal axis represents the sample name at different reaction times, and the vertical axis, Production, represents the amount of hydrogen and oxygen produced (μmol·h⁻¹). -1 ). Detailed Implementation

[0024] First, 10 mL of an aqueous solution containing 0.7 g SrCl₂·6H₂O was mixed with 30 mL of an aqueous solution containing 4 g LiOH·H₂O and stirred for 30 min to obtain solution A. In an ice-water bath, 0.26 mL of TiCl₄ was added to 25 mL of deionized water containing 2 g 1,2-propanediol and stirred for 5 min to obtain solution B. Then, solutions A and B were mixed and stirred for 30 min. The resulting mixture was then transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and heated in a 200 °C oven for 36 h. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The sample was centrifuged and washed several times with deionized water, then dried overnight at 60 °C to obtain SrTiO₃ with different exposed crystal planes.

[0025] A heterostructure was constructed by growing TiO2 on the (001) crystal plane of SrTiO3 through hydrothermal etching with hydrochloric acid. 200 mg of SrTiO3 was dissolved in 50 mL of a 0.01 M HCl solution and sonicated for 2 min. The solution was then transferred to a 100 mL PTFE-lined stainless steel autoclave and heated in an oven at 200 °C. The resulting samples were washed multiple times with water and then dried at 60 °C. The synthesized samples were named STO-x (x = 12 h, 36 h, 72 h, where x represents the hydrothermal reaction time).

[0026] The present invention will now be further described in detail with reference to embodiments and accompanying drawings.

[0027] Example 1

[0028] Solution A, obtained by mixing an aqueous solution of SrCl2·6H2O with an aqueous solution of LiOH·H2O, was mixed with TiCl4 in a 1,2-propanediol solution to obtain solution B. The mixture was stirred and hydrothermally reacted for a period of time to obtain SrTiO3. Then, a series of nested SrTiO3 / TiO2 heterojunctions were obtained by hydrothermal etching with hydrochloric acid for different times as the research object. Their morphology and charge space separation were studied.

[0029] Morphology characterization equipment: A Regulus 8100 field emission scanning electron microscope was used to observe the surface morphology of the material. For example... Figure 1 As shown, SrTiO3 / TiO2 has an octahedral morphology and is uniform in size, with a particle size of approximately 400 nm. Figure 1 As shown in Figure a, the original SrTiO3 surface is smooth, exposing the (001) and (110) crystal planes, respectively; after etching with hydrochloric acid, cone-shaped small particles grow on the SrTiO3 surface. Figure 1 In step b, it can be clearly seen that the particles only grow on the (001) crystal plane, the particle size is small, and the growth is dense; as the etching time increases, the size of the TiO2 particles on the SrTiO3 surface gradually increases, and it is observed that some TiO2 exists inside the SrTiO3 and is exposed from the (001) crystal plane. Figure 1 (cd); also, as... Figure 2 As shown, through the co-catalysts Au and MnO x The deposition locations also reveal charge space separation.

[0030] Example 2

[0031] Solution A, obtained by mixing an aqueous solution of SrCl2·6H2O with an aqueous solution of LiOH·H2O, was mixed with TiCl4 in a 1,2-propanediol solution to obtain solution B. The mixture was stirred and hydrothermally reacted for a period of time to obtain SrTiO3. Then, a series of nested SrTiO3 / TiO2 heterojunctions were obtained by hydrothermal etching with hydrochloric acid for different times as the research object. The phase composition was studied by Raman spectroscopy.

[0032] Raman testing equipment and conditions: Labram HR-800. For example... Figure 2 As shown, the original STO was at 176 cm. -1 A distinct peak exists at this location, corresponding to the first-order vibrational mode of SrTiO3. For the etched sample, at 144 cm⁻¹... -1 A new and distinct characteristic peak appears at this point, which is one of the characteristic peaks of anatase TiO2 and is an E peak of TiO2. gThe pattern corresponds to the symmetric stretching vibration of the Ti-O bond. In the magnified image on the right, the characteristic peak intensity of TiO2 gradually increases, while the characteristic peak intensity of SrTiO3 decreases, indicating that the TiO2 content gradually increases with the increase of hydrothermal reaction time.

[0033] Example 3

[0034] Solution A, obtained by mixing aqueous solutions of SrCl2·6H2O and LiOH·H2O, was mixed with solution B, obtained by adding TiCl4 to 1,2-propanediol solution and stirred for a period of time to obtain SrTiO3. The nested SrTiO3 / TiO2 heterojunction after hydrothermal etching with hydrochloric acid for 36 h was used as the research object to study its elemental distribution.

[0035] Elemental distribution characterization equipment: JEM-F200 is used to observe the distribution and composition of material elements. For example... Figure 3 As shown in the elemental mapping diagram, Sr elements are mostly distributed at the edges of SrTiO3, while the signal intensities of Ti and O elements inside are much greater than those at the edges of SrTiO3, fully demonstrating that some SrTiO3 inside the catalyst is converted into TiO2 particles. Furthermore, the signal intensities of Ti and O elements on the SrTiO3 surface correspond to the shape of SrTiO3, indicating the successful construction of the nested heterojunction.

[0036] Example 4

[0037] Solution A, obtained by mixing an aqueous solution of SrCl2·6H2O with an aqueous solution of LiOH·H2O, was mixed with TiCl4 in a 1,2-propanediol solution to obtain solution B. The mixture was stirred and hydrothermally reacted for a period of time to obtain SrTiO3. Then, a series of nested SrTiO3 / TiO2 heterojunctions were obtained by hydrothermal etching with hydrochloric acid for different times as the research object, and their photocatalytic performance was studied.

[0038] Photocatalytic water splitting conditions: 50 mg of photocatalyst was dispersed in 100 mL of deionized water. Under vacuum, 0.1% Rh, 0.075% Cr₂O₃, and 0.05% CoO₂ were sequentially photodeposited. x The photocatalytic overall water splitting experiment was tested using an all-glass automated online trace gas analysis system (Labsolar-6A). A 300 W Xe lamp was used as the light source, and the generated H2 and O2 were analyzed using an online gas chromatograph with Ar as the carrier gas (GC-2014).

[0039] The results of the examples demonstrate a method for preparing a nested SrTiO3 / TiO2 heterojunction photocatalytic material. This method involves growing TiO2 on the anisotropic SrTiO3(001) crystal plane to form a nested heterojunction. The construction of the heterojunction provides a stronger driving force for the transfer of photogenerated electrons and holes, reduces the recombination of photogenerated carriers in the bulk phase, and facilitates the migration of more carriers to the surface to participate in the reaction, thus improving the photocatalytic water splitting performance. Compared with existing methods for preparing SrTiO3 / TiO2 heterojunctions, this method is the first to synthesize a nested heterojunction, and the synthesis steps are simple with mild reaction conditions. This method has guiding significance and potential for practical application in the preparation of more heterojunction photocatalytic materials in the future.

Claims

1. A method for preparing an in-situ etched and grown nested SrTiO3 / TiO2 heterojunction photocatalytic material. Specifically, an aqueous solution of SrCl2·6H2O and an aqueous solution of LiOH·H2O are mixed and stirred to obtain solution A. TiCl4 is added to a solution of 1,2-propanediol and stirred to obtain solution B. Solutions A and B are mixed and stirred and subjected to hydrothermal reaction for a period of time to obtain octahedral SrTiO3. After hydrothermal etching with hydrochloric acid, conical small particles are grown on the (001) crystal plane of SrTiO3. As the etching time increases, the size of TiO2 particles gradually increases and is exposed from the (001) crystal plane. After cooling, centrifugation, cleaning and drying, the in-situ etched and grown nested SrTiO3 / TiO2 heterojunction photocatalytic material can be obtained.

2. The method for preparing an in-situ etched growth nested SrTiO3 / TiO2 heterojunction photocatalytic material according to claim 1, characterized in that: SrCl2·6H2O and TiCl4 were used as Sr source and Ti source, respectively; LiOH·H2O and 1,2-propanediol were used together as crystal facet growth control agents.

3. The method for preparing an in-situ etched growth nested SrTiO3 / TiO2 heterojunction photocatalytic material according to claim 2, characterized in that: Dissolve 0.5–1.2 g SrCl2·6H2O in 10–24 mL of deionized water, and dissolve 4–8 g LiOH·H2O in 30–60 mL of deionized water to obtain solution A; in an ice-water bath, add 0.26–0.52 mL TiCl4 to 25–50 mL of deionized water containing 2–4 g 1,2-propanediol.

4. The method for preparing an in-situ etched growth nested SrTiO3 / TiO2 heterojunction photocatalytic material according to claim 1, characterized in that: After mixing and stirring solutions A and B for 30 min, the mixture was subjected to hydrothermal reaction at 180-200 °C for 12-36 h. The mixture was then dried and collected to obtain SrTiO3 with exposed (001) and (110) crystal planes.

5. The method for preparing an in-situ etched growth nested SrTiO3 / TiO2 heterojunction photocatalytic material according to claim 1, characterized in that: TiO2 was grown on the SrTiO3(001) crystal plane by hydrothermal etching with hydrochloric acid at a concentration of 0.01~0.05 M.

6. The method for preparing an in-situ etched growth nested SrTiO3 / TiO2 heterojunction photocatalytic material according to claim 1, characterized in that: Dissolve 200-400 mg of SrTiO3 in 50 mL of hydrochloric acid solution of a specific concentration and react under hydrothermal conditions at 180-220℃ for 12-36 h.

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