Core-shell nanoflower BaTiO3 / In2S3 heterojunction with S-type energy band structure as well as preparation method and application of core-shell nanoflower BaTiO3 / In2S3 heterojunction

Abstract

The invention discloses a core-shell nanoflower BaTiO3 / In2S3 heterojunction with an S-type energy band structure as well as a preparation method and application of the core-shell nanoflower BaTiO3 / In2S3 heterojunction. The preparation method comprises the following steps: step 1, preparing carboxylated BaTiO3 nanoparticles; step 2, adding carboxylated BaTiO3 nanoparticles, indium salt, C2H5NS and CH4N2O into distilled water, and stirring on a magnetic stirrer to obtain a first mixed solution; 3, transferring the first mixed solution into a high-pressure kettle, and carrying out heating reaction to obtain a second mixed solution; step 4, naturally cooling the second mixed solution to room temperature, washing, centrifuging and drying to obtain a BaTiO3 / In2S3 heterojunction; the core-shell nanoflower BaTiO3 / In2S3 heterojunction with the S-type energy band structure is used as a photocatalyst to be applied to degradation of doxycycline hydrochloride, degradation of rhodamine B and reduction of Cr (VI), and a good degradation effect can be obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic materials, and particularly relates to a core-shell nanoflower BaTiO3 / In2S3 heterojunction with an S-type energy band structure, and a preparation method and application thereof. Background Art

[0002] With the acceleration of the global industrialization and urbanization processes, water pollution has become a major challenge threatening the ecological environment and human health. Complex pollutants such as heavy metal ions and organic dyes in industrial wastewater, pesticides and fertilizers remaining in agricultural activities, antibiotics and microplastics in domestic sewage, etc. have led to water eutrophication and the accumulation of toxic substances. Traditional physical adsorption, chemical oxidation, and biodegradation technologies are ineffective in dealing with refractory emerging pollutants (such as persistent organic pollutants like antibiotics, dyes, heavy metals, etc.) due to defects such as low efficiency, high cost, and easy generation of secondary pollution. In this context, photocatalytic technology driven by solar energy is regarded as an ideal alternative due to its green and sustainable characteristics. However, traditional photocatalysts (such as TiO2) have bottlenecks such as a narrow light absorption range (only responding to ultraviolet light), a high carrier recombination rate, and poor stability, which severely restricts their practical applications. Summary of the Invention

[0003] One object of the present invention is to provide a core-shell nanoflower BaTiO3 / In2S3 heterojunction with an S-type energy band structure, which has high photocatalytic degradation ability and reduction activity, and can improve the catalytic efficiency.

[0004] Another object of the present invention is to provide a preparation method of a core-shell nanoflower BaTiO3 / In2S3 heterojunction with an S-type energy band structure. The core-shell nanoflower BaTiO3 / In2S3 heterojunction with an S-type energy band structure is prepared by a hydrothermal method. The preparation method is simple, has a high preparation efficiency, and a low preparation cost.

[0005] The present invention also provides an application of a core-shell nanoflower BaTiO3 / In2S3 heterojunction with an S-type energy band structure. The core-shell nanoflower BaTiO3 / In2S3 heterojunction with an S-type energy band structure is used as a photocatalyst in the degradation of doxycycline hydrochloride, the degradation of rhodamine B, and the reduction of Cr(VI) reaction.

[0006] The technical solution provided by the present invention is as follows:

[0007] A preparation method of a core-shell nanoflower BaTiO3 / In2S3 heterojunction with an S-type energy band structure, comprising the following steps:

[0008] Step 1: Prepare carboxylated BaTiO3 nanoparticles;

[0009] Step 2: After adding the carboxylated BaTiO3 nanoparticles, indium salt, C2H5NS, and CH4N2O into distilled water, stir on a magnetic stirrer to obtain a first mixed solution;

[0010] Step 3: Transfer the first mixed solution into an autoclave, heat and react to obtain a second mixed solution;

[0011] Step 4: Naturally cool the second mixed solution to room temperature, wash, centrifuge, and dry it to obtain the BaTiO3 / In2S3 heterojunction.

[0012] Preferably, in Step 1, the method for preparing the carboxylated BaTiO3 nanoparticles is as follows:

[0013] Add succinic anhydride to DMF, stir to dissolve, then dropwise add 3-aminopropyltriethoxysilane. After stirring the obtained mixture at room temperature, add deionized water, DMF, and BaTiO3, stir again at room temperature, wash three times with distilled water and ethanol respectively, and dry at 80 °C to obtain the carboxylated BaTiO3 nanoparticles.

[0014] Preferably, in Step 2, the molar ratio of the carboxylated BaTiO3 nanoparticles, InCl3·4H2O, C2H5NS, CH4N2O, and distilled water is 17:100:200:200:450.

[0015] Preferably, in Step 2, the stirring speed is 500 rpm and the stirring time is 30 min.

[0016] Preferably, the autoclave is an autoclave with a polytetrafluoroethylene liner.

[0017] Preferably, in Step 3, heat and react at a temperature of 15**0**C - 180 °C for 10 h - 12 h to obtain a second mixed solution.

[0018] Preferably, in Step 4, wash three times with distilled water and ethanol in sequence, and dry at 60 °C for 10 h - 12 h to obtain the BaTiO3 / In2S3 heterojunction.

[0019] A core-shell nanoflower BaTiO3 / In2S3 heterojunction with an S-type energy band structure is prepared by using the preparation method of the core-shell nanoflower BaTiO3 / In2S3 heterojunction with an S-type energy band structure.

[0020] The invention discloses an application of a core-shell nanoflower BaTiO3 / In2S3 heterojunction with an S-type energy band structure. The core-shell nanoflower BaTiO3 / In2S3 heterojunction with an S-type energy band structure is used as a photocatalyst in the degradation of doxycycline hydrochloride, the degradation of rhodamine B and the reduction of Cr(VI).

[0021] The beneficial effects of the present invention are:

[0022] The present invention constructs a flower-shaped In2S3 array on the surface of carboxyl-modified BaTiO3 nanoparticles (BTO NPs, particle size of about 200 nm) by an in situ growth method, forming a core-shell heterojunction (BaTiO3 / In2S3) with BTO as the core and In2S3 as the shell; the performance improvement of this structure includes the following three aspects: (1) Band synergy optimization: the wide spectral response characteristics of BaTiO3 and the high visible light absorption efficiency of In2S3 complement each other, extending the light absorption range to the entire UV-visible spectrum; (2) S-type heterojunction charge transfer path: a built-in electric field is formed at the interface, driving the directional migration of photogenerated electrons from In2S3 to BaTiO3 and the reverse transfer of holes, significantly suppressing carrier recombination and retaining strong redox ability; (3) Core-shell nanoflower morphology advantage: the three-dimensional flower-like structure provides a high specific surface area and abundant active sites, enhancing pollutant adsorption and reaction kinetics. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is a scanning electron microscope and a transmission electron microscope photograph of the BaTiO 3 / In 2 S 3 heterojunction prepared in an embodiment of the present invention.

[0024] FIG1( a ) is a scanning electron microscope image of In2S3 described in the present invention.

[0025] FIG1( b ) is a scanning electron microscope image of the BaTiO 3 / In 2 S 3 heterojunction prepared in an embodiment of the present invention.

[0026] FIG1( c ) is a transmission electron micrograph of the BaTiO 3 / In 2 S 3 heterojunction prepared in an embodiment of the present invention.

[0027] FIG1( d ) is an EDS element mapping image of barium in the BaTiO 3 / In 2 S 3 heterojunction prepared in an embodiment of the present invention.

[0028] FIG1(e) is an EDS element mapping image of titanium in the BaTiO3 / In2S3 heterojunction prepared in an embodiment of the present invention.

[0029] FIG1(f) is an EDS element mapping image of oxygen in the BaTiO3 / In2S3 heterojunction prepared in an embodiment of the present invention.

[0030] Figure 1(g) is the EDS elemental mapping image of indium in the BaTiO3 / In2S3 heterojunction prepared in the embodiment of the present invention.

[0031] Figure 1(h) is the EDS elemental mapping image of sulfur in the BaTiO3 / In2S3 heterojunction prepared in the embodiment of the present invention.

[0032] Figure 2 are the X-ray diffraction patterns of BaTiO3, In2S3 and the BaTiO3 / In2S3 heterojunction prepared in the embodiment of the present invention.

[0033] Figure 3 are the infrared spectroscopy analysis diagrams of BaTiO3, In2S3 and the BaTiO3 / In2S3 heterojunction prepared in the embodiment of the present invention.

[0034] Figure 4 are the concentration change diagrams of the degradation of DH (doxycycline hydrochloride), degradation of RhB (rhodamine B) and reduction of Cr(VI) by the BaTiO3 / In2S3 heterojunction prepared in the embodiment of the present invention.

[0035] Figure 5 are the kinetic curves of the degradation of DH (doxycycline hydrochloride), degradation of RhB (rhodamine B) and reduction of Cr(VI) by the BaTiO3 / In2S3 heterojunction prepared in the embodiment of the present invention. <x

[0036] Figure 6 are the concentration change diagrams of the photocatalytic reduction of Cr(VI) by the BaTiO3 / In2S3-(1:3) prepared in the embodiment of the present invention and the BaTiO3 / In2S3-(1:1) heterojunction prepared in the comparative example.

[0037] Figure 7 are the kinetic curves of the photocatalytic reduction of Cr(VI) by the BaTiO3 / In2S3-(1:3) prepared in the embodiment of the present invention and the BaTiO3 / In2S3-(1:1) heterojunction prepared in the comparative example.

[0038] Figure 8 are the XRD spectra of the BaTiO3 / In2S3 heterojunction before and after three-cycle tests in the BaTiO3 / In2S3 heterojunction prepared in the embodiment of the present invention.

[0039] Figure 9 is the photocatalytic mechanism diagram of the present invention.

[0040] Figure 9 (A) is the energy band structure of the BaTiO3 / In2S3 heterojunction described in the present invention.

[0041] Figure 9(B) Band-edge bending and built-in electric field at the contact interface of the BaTiO3 / In2S3 heterojunction according to the present invention in the dark.

[0042] Figure 9 (C) Mechanism of BaTiO3 / In2S3 S-type heterojunction for degrading DH under light illumination in the BaTiO3 / In2S3 heterojunction according to the present invention. Detailed implementation manners

[0043] The following further elaborates on the present invention with reference to the accompanying drawings so that those skilled in the art can implement it according to the text of the specification.

[0044] Barium titanate (BaTiO3), as a typical piezoelectric material, has shown great potential in the field of photocatalysis in recent years because its internal spontaneous polarization field can effectively drive the separation of photo-generated electron-hole pairs and inhibit carrier recombination. Indium sulfide (In2S3), as a narrow-bandgap semiconductor (bandgap energy 2.0 - 2.5 eV), has significant advantages: Firstly, its bandgap position is in the ideal range of visible light absorption, and it can capture approximately 45% of the visible light energy in the solar spectrum to achieve efficient photon absorption and electron-hole pair generation; Secondly, its carrier mobility is significantly higher than that of traditional metal sulfides and oxides, which can accelerate the charge transfer to the catalyst surface to participate in the reaction; Thirdly, its inherent chemical stability can resist corrosion under aqueous environments and strong reaction conditions, ensuring long-term recyclability. Compared with existing photocatalytic materials, In2S3 shows obvious superiority in terms of light absorption efficiency, carrier transport ability, and stability.

[0045] Based on the above characteristics, the present invention provides a preparation method for a core-shell nanoflower BaTiO3 / In2S3 heterojunction with an S-type energy band structure, and the specific implementation process is as follows.

[0046] I. Preparation of carboxylated BaTiO3 nanoparticles (Car-BaTiO3).

[0047] As a preference, the method for preparing carboxylated BaTiO3 nanoparticles is: adding succinic anhydride to DMF, stirring and dissolving it, then dropwise adding 3-aminopropyltriethoxysilane. After stirring the obtained mixture at room temperature, adding deionized water, DMF, and BaTiO3, stirring again at room temperature, washing three times with distilled water and ethanol respectively, and drying at 80 °C to obtain carboxylated BaTiO3 nanoparticles.

[0048] II. After adding the carboxylated BaTiO3 nanoparticles, indium salt, C2H5NS, and CH4N2O to distilled water, stir on a magnetic stirrer to obtain a first mixed solution.

[0049] Among them, the stirring speed is 500 rpm and the stirring time is 30 min.

[0050] Preferably, the molar ratio of carboxylated BaTiO3 nanoparticles, InCl3·4H2O, C2H5NS, CH4N2O and distilled water is: 17:100:200:200:450.

[0051] III. Transfer the first mixed solution into an autoclave with a polytetrafluoroethylene lining, and heat and react at a temperature of 150°C to 180°C for 10 h to 12 h to obtain a second mixed solution.

[0052] IV. Naturally cool the second mixed solution to room temperature, and obtain the BaTiO3 / In2S3 heterojunction after washing, centrifuging and drying.

[0053] Preferably, wash with distilled water and ethanol three times in sequence, and dry at 60°C for 10 h to 12 h to obtain the BaTiO3 / In2S3 heterojunction.

[0054] The present invention also provides a core-shell nanoflower BaTiO3 / In2S3 heterojunction with an S-type energy band structure, which is prepared by using the preparation method of the core-shell nanoflower BaTiO3 / In2S3 heterojunction with an S-type energy band structure.

[0055] The present invention also provides an application method of a core-shell nanoflower BaTiO3 / In2S3 heterojunction with an S-type energy band structure. The core-shell nanoflower BaTiO3 / In2S3 heterojunction with an S-type energy band structure is used as a photocatalyst in the reactions of degrading doxycycline hydrochloride, degrading rhodamine B and reducing Cr(VI).

[0056] The present invention provides a method for constructing a flower-like In2S3 array on the surface of carboxyl-modified BaTiO3 nanoparticles (BTO NPs, particle size about 200 nm) by in-situ growth method to form a core-shell heterojunction (BaTiO3 / In2S3) with BTO as the core and In2S3 as the shell. The performance of this heterojunction structure is improved through the following mechanisms: (1) Energy band synergistic optimization: The broadband spectral response characteristics of BaTiO3 are complementary to the high visible light absorption efficiency of In2S3, extending the light absorption range to the entire ultraviolet-visible spectrum; (2) S-type heterojunction charge transport path: A built-in electric field is formed at the interface, driving the photogenerated electrons to migrate directionally from In2S3 to BaTiO3, and the holes transfer in the reverse direction, significantly inhibiting the carrier recombination and retaining strong redox ability; (3) Core-shell nanoflower morphology advantage: The three-dimensional flower-like structure provides a high specific surface area and abundant active sites, enhancing the pollutant adsorption and reaction kinetics performance.

[0057] The heterojunction material prepared by a one-step hydrothermal method exhibits excellent photocatalytic performance in experiments and still maintains high stability after recycling. This efficient and low-cost preparation process provides an innovative solution for the deep purification of industrial wastewater and medical wastewater, and has broad prospects for environmental governance and industrial application.

[0058] The preparation method and application effect of the core-shell nanosheet BaTiO3 / In2S3 heterojunction with an S-type energy band structure provided by the present invention will be further described below in conjunction with specific embodiments.

[0059] Embodiment

[0060] After adding 1 mmol of succinic anhydride to 171.8 mmol of DMF and stirring until dissolved, 2 mmol of 3-aminopropyltriethoxysilane was added dropwise. The resulting mixture was stirred at room temperature for 3 h, and then, 0.33 mmol of deionized water, 21.57 mmol of DMF, and 0.13 mmol of BaTiO3 were added and stirred at room temperature for 6 h. It was washed three times with distilled water and ethanol respectively and dried overnight at 80 °C to obtain carboxylated BaTiO3, denoted as Car-BaTiO3.

[0061] 1 mmol of InCl3·4H2O, 2 mmol of C2H5NS, 2 mmol of CH4N2O, and 0.17 mmol of Car-BaTiO3 were added to 4.5 mmol of H2O to form a homogeneous solution. After stirring at room temperature for 30 min, it was transferred to a 100 mL autoclave lined with polytetrafluoroethylene, heated to 180 °C, and reacted for 12 h. After naturally cooling to room temperature, it was washed 3 times with H2O and ethanol, centrifuged, and dried at 60 °C for 12 h to obtain the BaTiO3 / In2S3-(1:3) heterojunction.

[0062] Comparative Example

[0063] After adding 1 mmol of succinic anhydride to 171.8 mmol of DMF and stirring until dissolved, 2 mmol of 3-aminopropyltriethoxysilane was added dropwise. The resulting mixture was stirred at room temperature for 3 h, and then, 0.33 mmol of deionized water, 21.57 mmol of DMF, and 0.13 mmol of BaTiO3 were added and stirred at room temperature for 6 h. It was washed three times with distilled water and ethanol respectively and dried overnight at 80 °C to obtain carboxylated BaTiO3, denoted as Car-BaTiO3.

[0064] 1 mmol of InCl3·4H2O, 2 mmol of C2H5NS, 2 mmol of CH4N2O and 0.5 mmol of Car-BaTiO3 were added to 4.5 mmol of H2O to form a homogeneous solution. After stirring at room temperature for 30 min, the solution was transferred into a 100 mL autoclave lined with polytetrafluoroethylene and heated to 180 °C for 12 h. After natural cooling to room temperature, the product was washed three times with H2O and ethanol successively, centrifuged, and dried at 60 °C for 12 h to obtain the BaTiO3 / In2S3-(1:1) heterojunction.

[0065] As shown in Fig. 1(a) and Fig. 1(b), the morphology and structure of the samples prepared in the examples were observed by SEM. It can be observed that pure In2S3 consists of aggregates composed of many nanosheets. Car-BaTiO3 and In2S3 nanosheets were mixed in a suspension, and a tightly bound BaTiO3 / In2S3 heterojunction was obtained through interaction. From the TEM image of the BaTiO3 / In2S3 heterojunction in Fig. 1(c), it can be clearly seen that many irregular In2S3 nanosheets surround the spherical Car-BaTiO3, indicating that In2S3 was successfully prepared on the surface of Car-BaTiO3. The EDS elemental mapping images in Fig. 1(d)–(h) show that the elements Ba, Ti, O, In, and S are evenly distributed on the surface of BaTiO3 / In2S3, confirming that the uniform attachment of In2S3 on BaTiO3 exhibits uniform structural characteristics, which can lead to the formation of more active sites between the two materials and enhance the catalytic ability of the composite material.

[0066] As Figure 2As shown, for pure In2S3, based on the standard card (JCPDS#84-1385), the diffraction peaks at 14.32°, 23.39°, 27.50°, 33.24°, 43.59°, and 47.77° correspond to the (111), (220), (311), (400), (511), and (440) planes of the In2S3 standard pattern (PDF:), respectively. For BaTiO3, the characteristic diffraction peaks at 44.9° and 45.4° (JCPDS#76-0744) indicate that BaTiO3 exists in the tetragonal phase. Its diffraction peaks at 22.237°, 31.495°, 38.893°, 45.371°, and 56.275° correspond to the (100), (101), (111), (200), and (211) diffraction planes, respectively. For the heterojunction composite material prepared in the examples, the XRD pattern clearly shows the mixed diffraction peaks of In2S3 and BaTiO3, and the diffraction peak intensity of the main peak changes along with the change of the mass ratio of In2S3 and BaTiO3. For example, as the content of In2S3 increases, the intensity of the diffraction peak (200) of BaTiO3 gradually decreases, while the diffraction peak intensity of In2S3 increases rapidly. In short, the XRD results confirm that In2S3 and BaTiO3 do coexist in the composite photocatalyst, and no impure phase is observed in all samples.

[0067] Fourier transform infrared spectroscopy (FTIR) was used to confirm the heterojunction structure prepared in the examples, and the results are as Figure 3 shown. For BaTiO3, the two typical absorption peaks at 541 and 428 cm -1 are respectively attributed to the stretching and bending vibrations of Ti-O in BaTiO3. The peak at 1452 cm -1 corresponds to the vibration of Ba-Ti-O. For In2S3, the peak at 1391 cm -1 corresponds to the vibration of In-S. The diffraction peaks at 3400 cm -1 and 1600 cm -1 are O-H vibration peaks, and the diffraction peaks at 2800 cm -1 and 2900 cm -1 are C-H vibration peaks. It is worth noting that the diffraction peaks corresponding to Ti-O, Ba-Ti-O, and In-S appear in the composite catalyst BaTiO3 / In2S3, indicating that In2S3 is successfully compounded with BaTiO3, and the prepared samples are relatively pure.

[0068] As Figure 4 shown, in order to investigate the degradation effects of the BaTiO3 / In2S3 catalyst prepared in the examples on DH, RhB, and Cr(Ⅵ) respectively within 30 min, a graph of the change in pollutant concentration was plotted, where Ct C and C0 represent the instantaneous and initial concentrations of pollutants in the aqueous solution, respectively. This indicates that there is a synergistic effect between BaTiO3 and In2S3. When they act on DH, RhB, and Cr(Ⅵ) respectively, the change in the degradation rate can be clearly seen. This effect may be due to the interaction between the two materials, such as the matching of the energy band structure, the effective separation of electron-hole pairs, etc., thereby improving the utilization efficiency of photogenerated carriers and the photocatalytic activity.

[0069] As Figure 5 shown, in order to investigate the photocatalytic degradation kinetics of the BaTiO3 / In2S3 catalyst prepared in the examples on DH, RhB, and Cr(Ⅵ), the first-order kinetic equation ln(C t / C0) = kt was used for simulation calculation. Where C t and C0 represent the instantaneous and initial concentrations of pollutants in the aqueous solution, respectively. k represents the degradation rate constant. The degradation of DH, RhB, and Cr(Ⅵ) by the BaTiO3 / In2S3 catalyst conforms to the first-order kinetic model, and the degradation rate constants are k: DH = 0.03142 min -1 , RhB = 0.07137 min -1 , Cr(Ⅵ) = 0.14245 min -1 . This indicates that the combination of BaTiO3 and In2S3 can effectively improve the photocatalytic efficiency, and it also shows that a heterojunction is formed in the composite material BaTiO3 / In2S3. This result is consistent with the above photocatalytic degradation experiment.

[0070] As Figure 6 shown, the BaTiO3 / In2S3 catalysts prepared in the examples and comparative examples were respectively used for the degradation of Cr(Ⅵ), and a graph of the change in pollutant concentration was plotted. Where C t and C0 represent the instantaneous and initial concentrations of pollutants in the aqueous solution, respectively. It can be seen from Figure 6 that the degradation rate of Cr(Ⅵ) using BaTiO3 / In2S3-(1:3) prepared in the example is 99%, and the degradation rate of Cr(Ⅵ) using BaTiO3 / In2S3-(1:1) prepared in the comparative example is 85%. It is proved that the reduction effect of BaTiO3 / In2S3-(1:3) prepared in the example on Cr(Ⅵ) is better than that of BaTiO3 / In2S3-(1:1) prepared in the comparative example on Cr(Ⅵ). By reasonably setting the ratio of BaTiO3 and In2S3 in the example, the photocatalytic reduction ability is further enhanced.

[0071] As Figure 7 shown, in order to investigate the kinetics of the BaTiO3 / In2S3 catalysts prepared in the examples and comparative examples on Cr(Ⅵ), the first-order kinetic equation ln(Ct / C0) = kt for simulation calculation. Where C t and C0 represent the instantaneous and initial concentrations of pollutants in the aqueous solution respectively. k represents the degradation rate constant. The reduction of Cr(Ⅵ) by the BaTiO3 / In2S3 catalyst conforms to the first-order kinetic model, and the degradation rate constants are k: BaTiO3 / In2S3-(1:1) = 0.05972 min -1 、BaTiO3 / In2S3-(1:3) = 0.14245 min -1 . It shows that the BaTiO3 / In2S3-(1:3) prepared in the examples has a better degradation rate for pollutants than the BaTiO3 / In2S3-(1:1) prepared in the comparative examples.

[0072] As Figure 8 shown, after three-cycle degradation experiments, the photocatalytic degradation activity of the BaTiO3 / In2S3 prepared in the examples decreased slightly. XRD analysis was carried out on the BaTiO3 / In2S3 prepared in the examples, and the results showed that the structure of BaTiO3 / In2S3 could still remain stable after photocatalytic degradation.

[0073] As Figure 9 (A) shown, compared with BaTiO3 as the OSP, In2S3 as the RSP has a smaller work function and a higher Fermi level. When BaTiO3 and In2S3 contact and form a heterojunction, electrons will flow from In2S3 with a higher Fermi level to BaTiO3 to reach the equilibrium Fermi level, which generates a built-in electric field from In2S3 to BaTiO3. As Figure 9 (B) the energy bands bend (upward for In2S3 and downward for BaTiO3 respectively). It should be noted that there are four regions with different charge distribution densities in the heterojunction, which are in turn: the bulk of BaTiO3, the interface of BaTiO3, the interface of In2S3, and the bulk of In2S3. The built-in electric field (IEF) only acts on the interface and has no significant effect on the Fermi level of the deeper semiconductor. As Figure 9 (C) when irradiated, electrons in both semiconductors are photoexcited from the VB to the CB. Driven by the built-in electric field, the bent energy bands and electrostatic repulsion, the photogenerated electrons transfer from the CB of BaTiO3 to the VB of In2S3 to recombine with holes. On the contrary, the electrons in the CB of In2S3 and the holes in the VB of BaTiO3 transfer from the inside to the surface under the action of IEF, the bent energy bands and electrostatic repulsion. Therefore, these electrons and holes available for redox reactions are spatially separated, and the useless electrons and holes are eliminated, which ensures the high redox capacity of the system.

[0074] The preparation method of BaTiO3 / In2S3 provided by the present invention is simple, safe, and low in energy consumption. There are no toxic solvents during the preparation process, which is green and environmentally friendly. It demonstrates high-efficiency photocatalytic degradation of doxycycline hydrochloride, degradation of rhodamine B, and reduction of Cr(VI), and the cost and photocatalytic efficiency have important industrial application values.

[0075] Although the embodiments of the present invention have been disclosed as above, they are not limited to only the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the illustrated examples here.

Claims

1. A preparation method of a core-shell nanosized flower BaTiO3 / In2S3 heterojunction with an S-shaped energy band structure, characterized in that, It includes the following steps: Step 1, prepare carboxylated BaTiO3 nanoparticles; Step 2, add the carboxylated BaTiO3 nanoparticles, indium salt, C2H5NS and CH4N2O into distilled water, and stir on a magnetic stirrer to obtain a first mixed solution; Step 3, transfer the first mixed solution into an autoclave, heat and react to obtain a second mixed solution; Step 4, naturally cool the second mixed solution to room temperature, wash, centrifuge and dry it to obtain a BaTiO3 / In2S3 heterojunction.

2. The preparation method of the core-shell nanosized flower BaTiO3 / In2S3 heterojunction with an S-shaped energy band structure according to claim 1, characterized in that, In the said Step 1, the method for preparing carboxylated BaTiO3 nanoparticles is as follows: Add succinic anhydride into DMF, stir and dissolve it, then dropwise add 3-aminopropyltriethoxysilane. After stirring the obtained mixture at room temperature, add deionized water, DMF and BaTiO3, stir again at room temperature, wash 3 times with distilled water and ethanol respectively, and dry at 80 °C to obtain carboxylated BaTiO3 nanoparticles.

3. The preparation method of the core-shell nanosized flower BaTiO3 / In2S3 heterojunction with an S-shaped energy band structure according to claim 2, characterized in that, In the said Step 2, the molar ratio of the carboxylated BaTiO3 nanoparticles, InCl3·4H2O, C2H5NS, CH4N2O and distilled water is 17:100:200:200:

450.

4. The preparation method of the core-shell nanosized flower BaTiO₃ / In₂S₃ heterojunction with an S-shaped energy band structure according to claim 3, characterized in that, In the said Step 2, the stirring speed is 500 rpm and the stirring time is 30 min.

5. The preparation method of the core-shell nanosized flower BaTiO3 / In2S3 heterojunction with an S-shaped energy band structure according to claim 4, characterized in that, The autoclave uses an autoclave with a polytetrafluoroethylene inner liner.

6. The preparation method of the core-shell nanosized flower BaTiO3 / In2S3 heterojunction with an S-shaped energy band structure according to any one of claims 1-5, characterized in that, In the said Step 3, heat and react at a temperature of 150 °C to 180 °C for 10 h to 12 h to obtain a second mixed solution.

7. The preparation method of the core-shell nanosized flower BaTiO3 / In2S3 heterojunction with an S-shaped energy band structure according to claim 6, characterized in that, In the said Step 4, wash 3 times with distilled water and ethanol in sequence, and dry at 60 °C for 10 h to 12 h to obtain a BaTiO3 / In2S3 heterojunction.

8. A core-shell nanosized flower BaTiO3 / In2S3 heterojunction with an S-shaped energy band structure, characterized in that, Prepare by using the preparation method of the BaTiO3 / In2S3 heterojunction of the core-shell nanosflower with an S-type energy band structure as described in any one of claims 1-7.

9. Application of a core-shell nanosized flower BaTiO3 / In2S3 heterojunction with an S-shaped energy band structure, characterized in that, Use the BaTiO3 / In2S3 heterojunction of the core-shell nanosflower with an S-type energy band structure as described in claim 8 as a photocatalyst in the reactions of degrading doxycycline hydrochloride, degrading rhodamine B and reducing Cr(VI).

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