Double-S-type heterojunction composite material and preparation method and application thereof

Abstract

The invention provides a double-S type heterojunction composite material as well as a preparation method and application thereof, the heterojunction composite material comprises a TiO2 nano-sheet, and Na < + >-Bi2O3 nano-particles are loaded on the surface of the TiO2 nano-sheet. According to the invention, Na < + >-Bi2O3 nanoparticles grow on a specific crystal face of a {101} / {001} crystal face co-exposed anatase TiO2 nanosheet in an oriented manner, so that the TiO2 {101} / Na < + >-Bi2O3 bifunctional photocatalyst with a double-S-type heterojunction structure is constructed, and the problems of single charge transfer path and high recombination rate of a traditional single-S-type heterojunction can be solved; and meanwhile, the limitation that a ternary double-S-type heterojunction preparation process is complicated and the interface controllability is poor is broken through, so that efficient separation and migration of photon-generated carriers are realized. The heterojunction composite material disclosed by the invention has excellent activity of photocatalytic decomposition of water to produce hydrogen, and in addition, the heterojunction composite material also shows excellent performance in synergic photocatalytic hydrogen production and tetracycline degradation application.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, specifically relating to a double S-type heterojunction composite material, its preparation method, and its application. Background Technology

[0002] Photocatalysis, as a sustainable energy conversion and environmental governance strategy, relies on the core mechanism of photogenerated carrier separation and migration processes in semiconductor materials. In solar-driven redox reactions, water splitting to produce hydrogen (2e⁻) is a key component. - +2H + → H2) and pollutant degradation represent two important application directions of this technology in energy conversion and environmental governance, respectively. However, a key scientific problem facing traditional photocatalytic systems is: the water oxidation reaction (2H2O + 4h) + → O2 + 4H + The thermodynamic barrier and slow kinetics of photocatalysis severely limit overall efficiency. While conventional strategies involving the introduction of organic sacrificial agents (such as triethanolamine and methanol) can promote carrier separation, they pose risks of high operating costs and secondary pollution. To address this challenge, researchers have proposed an innovative approach that couples the degradation of organic pollutants with photocatalytic hydrogen production. By utilizing pollutants as hole sacrificial agents, this approach achieves the dual benefits of "treating waste with waste," providing important guidance for the development of novel multifunctional photocatalytic systems.

[0003] Among numerous environmental pollutants, tetracycline antibiotics (TCs) have become ideal research subjects due to their unique molecular characteristics. As typical broad-spectrum antibacterial drugs, TCs exhibit exceptional chemical stability in the environment, and their residues not only induce bacterial resistance but also pose ecological risks through the water cycle. Notably, the abundance of electron-donating groups (such as phenolic hydroxyl and amino groups) in the TC molecular structure allows them to function as both degradation targets and highly efficient electron donors in photocatalysis. This characteristic overcomes the limitations of traditional sacrificial agents, providing a molecular basis for constructing a synergistic "pollutant degradation-hydrogen production" system. Existing research has shown that intermediate products generated during TC degradation can sustainably provide electrons and protons, creating favorable conditions for developing photocatalytic systems with dual functions of environmental remediation and energy production.

[0004] To achieve efficient synergy between pollutant degradation and photocatalytic hydrogen production, heterojunction engineering has proven to be one of the most promising materials design strategies. Compared to traditional type II or Z-type heterojunctions, S-type heterojunctions, due to their unique band-matching mechanism and built-in electric field effect, can maintain excellent redox capabilities while promoting effective separation of photogenerated carriers. However, single-S-type heterojunction systems still suffer from inherent drawbacks such as a single charge transport path and a high carrier recombination rate. Based on the latest band engineering theory, the construction of double-S-type heterojunctions offers a new approach to address this bottleneck: by constructing a stepped carrier migration channel, not only can the spectral response range be broadened, but the charge separation efficiency can also be significantly improved by leveraging multiple interfacial electric field effects. It is worth noting that most of the currently reported double-S-type heterojunction systems employ complex ternary component structures, generally suffering from key problems such as insufficient controllability of interfacial contacts and complex fabrication processes. Therefore, how to simplify the structure and improve the performance of double-S-type heterojunctions through the design and optimization of novel material systems while maintaining their structural advantages has become an important scientific problem that urgently needs to be solved in the field of photocatalytic materials. Summary of the Invention

[0005] To overcome the problems existing in the prior art, one objective of this invention is to provide a double S-shaped heterojunction composite material. A second objective of this invention is to provide a method for preparing the aforementioned double S-shaped heterojunction composite material. A third objective of this invention is to provide applications of the aforementioned double S-shaped heterojunction composite material. A fourth objective of this invention is to provide another application of the aforementioned double S-shaped heterojunction composite material.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a double S-shaped heterojunction composite material comprising TiO2 nanosheets, wherein the surface of the TiO2 nanosheets is loaded with Na. + -Bi2O3 nanoparticles; the Na + -Bi₂O₃ nanoparticles are doped with Na + Bi2O3 nanoparticles.

[0007] Preferably, the TiO2 nanosheets are TiO2 nanosheets exposing the {001} and {101} crystal planes; the Na + -Bi2O3 nanoparticles are loaded on the {101} crystal plane of TiO2 nanosheets.

[0008] This invention innovatively achieves the precise construction of a double S-shaped heterojunction in a binary composite system. Through a crystal plane engineering strategy, Na is directionally grown on the specific {101} crystal plane of anatase TiO2 nanosheets with co-exposed {101} / {001} crystal planes. +Bi₂O₃ nanoparticles were successfully used to construct a TiO₂{101} / Na₂ structure with a double S-type heterojunction. + Bi2O3 bifunctional photocatalysts address the issues of single charge transport pathways and high recombination rates in traditional single S-type heterojunctions, while overcoming the limitations of complex fabrication processes and poor interface controllability in ternary double S-type heterojunctions, thereby achieving efficient separation and migration of photogenerated carriers. Furthermore, compared to amorphous surface-controlled TiO2 / Na... + -Bi2O3 nanosheets, TiO2{101} / Na constructed based on the {101} crystal plane + The performance of Bi₂O₃ double S-type heterojunction nanosheets in photocatalytic water splitting for hydrogen production is significantly improved. Furthermore, they also exhibit excellent performance in synergistic photocatalytic hydrogen production and tetracycline degradation applications.

[0009] More preferably, the {001} crystal plane length of the TiO2 nanosheet is 10~80 nm.

[0010] More preferably, the {001} crystal plane length of the TiO2 nanosheet is 20~50 nm.

[0011] More preferably, the {101} crystal plane width of the TiO2 nanosheet is 2~20 nm.

[0012] More preferably, the {101} crystal plane width of the TiO2 nanosheet is 4~10 nm.

[0013] Preferably, the Na + The particle size of the Bi2O3 nanoparticles is 1~10 nm.

[0014] More preferably, the Na + The particle size of the Bi2O3 nanoparticles is 1~4 nm.

[0015] A second aspect of the present invention provides a method for preparing the double S-shaped heterojunction composite material described in the first aspect, comprising the following steps: TiO2 nanosheets and NaBiO3 were added to water and reacted under ultraviolet-visible light irradiation; the solid product was collected after the reaction and dried to obtain the double S-type heterojunction composite material.

[0016] The preparation method of this invention utilizes the photoreduction properties of the {101} crystal plane of TiO2 nanosheets to convert Bi in strongly oxidizing NaBiO3. 5+ Restored to Bi 3+ The precipitate was directionally deposited on the {101} crystal plane of TiO2 nanosheets; finally, after centrifugation, washing, and air drying, TiO2{101} / Na was obtained. + -Bi2O3 double S-type heterojunction nanosheets.

[0017] Preferably, the molar ratio of Ti in the TiO2 nanosheets to Bi in NaBiO3 is (8~20):1.

[0018] More preferably, the molar ratio of Ti in the TiO2 nanosheets to Bi in NaBiO3 is (10~14):1.

[0019] Preferably, the wavelength of the ultraviolet-visible light is 320-780 nm.

[0020] Preferably, the intensity of the ultraviolet-visible light is 200-700 mW / cm². 2 .

[0021] Preferably, the reaction time is 60-200 min.

[0022] More preferably, the reaction time is 100-200 min.

[0023] More preferably, the reaction time is 110, 120, 130, 140, 150, 160, 170, 180, or 190 min.

[0024] Preferably, the TiO2 nanosheets are anatase titanium dioxide nanosheets with simultaneously exposed {001} crystal planes.

[0025] Preferably, the method for preparing the TiO2 nanosheets includes the following steps: Titanium source and hydrofluoric acid were mixed and stirred in an organic solution to obtain a reaction precursor; the reaction precursor was transferred to a reaction vessel for solvothermal reaction to obtain TiO2 nanosheets.

[0026] More preferably, the titanium source is selected from at least one of tetrabutyl titanate, titanium tetrachloride, and titanium sulfate.

[0027] More preferably, the molar ratio of the titanium source to hydrofluoric acid is 1:(4.5-6).

[0028] More preferably, the organic solvent is an alcohol solvent.

[0029] More preferably, the temperature of the solvothermal reaction is 150-220°C.

[0030] More preferably, the temperature of the solvothermal reaction is 160-200℃.

[0031] More preferably, the reaction time of the solvothermal reaction is 9-15 h.

[0032] More preferably, the reaction time of the solvothermal reaction is 10-14 h.

[0033] Preferably, the method further includes the following steps: first, dissolving TiO2 nanosheets in water, then ultrasonically treating them to ensure uniform dispersion, and then magnetically stirring to form a homogeneous solution; then dispersing NaBiO3 in the homogeneous solution.

[0034] Preferably, the drying is carried out in air.

[0035] Preferably, the drying temperature is 60-100°C.

[0036] The third aspect of this invention provides the application of the double S-shaped heterojunction composite material described in the first aspect in photocatalytic water splitting for hydrogen production.

[0037] Preferably, the application method includes the following steps: placing the double S-shaped heterojunction composite material in water, irradiating it with light, and collecting hydrogen gas.

[0038] More preferably, it also includes the use of triethanolamine (TEOA) as a sacrificial agent.

[0039] More preferably, it also includes the use of tetracycline as a hole sacrificial agent.

[0040] The fourth aspect of this invention provides the application of the double S-shaped heterojunction composite material described in the first aspect in the degradation of tetracycline antibiotics.

[0041] Preferably, the tetracycline antibiotics include oxytetracycline, chlortetracycline, doxycycline hydrochloride, minocycline, and levofloxacin hydrochloride.

[0042] Preferably, the application method includes the following steps: placing the double S-shaped heterojunction composite material in water containing tetracycline antibiotics and irradiating it with light to carry out a degradation reaction.

[0043] The beneficial effects of this invention are: This invention provides a TiO2{101} / Na + -Bi2O3 double S-type heterojunction nanosheets, the heterojunction being composed of TiO2 nanosheets and Na + -Bi2O3 nanoparticles composite, the TiO2{101} / Na + Bi₂O₃ double S-type heterojunction nanosheets significantly enhanced the activity of photocatalytic water splitting for hydrogen production, achieving a photocatalytic water splitting rate of 63.2 μmol·h⁻¹. 1 Furthermore, it also exhibits excellent performance in synergistic photocatalytic hydrogen production and tetracycline degradation applications.

[0044] The specific beneficial effects are as follows: (i) The heterojunction of the present invention is composed of TiO2 nanosheets and Na + It is composed of Bi2O3 nanoparticles, in which Na+ Interstitial doping plays a dual crucial role in the modification of Bi2O3: on the one hand, it narrows its band gap to about 2.10 eV, broadens the light absorption range, and optimizes its work function to about 4.00 eV, achieving band matching with TiO2 and creating thermodynamic conditions for constructing an S-type heterojunction; on the other hand, this doping strategy significantly reduces the rate-determining energy barrier of the photocatalytic hydrogen evolution reaction, thereby greatly promoting the hydrogen evolution reaction kinetics.

[0045] (II) This invention overcomes the design limitations of existing double S-type heterojunctions, which generally rely on complex ternary compositions. By directional growth on specific crystal planes, it successfully achieves the desired structure in TiO2 and Na... + A double S-type heterojunction was constructed in the Bi2O3 binary system. This design not only simplifies the material structure and preparation process, but also improves the controllability and reproducibility of the interfacial contact, providing new design inspiration for the application of heterojunction systems in the field of efficient photocatalysis.

[0046] (iii) The present invention also provides the above-mentioned TiO2{101} / Na + The preparation method of Bi₂O₃ double S-type heterojunction nanosheets is based on the symmetry and photoreduction properties of the TiO₂{101} crystal plane, which successfully induces Na₂O₃ crystals to form a double S-type heterojunction. + The directional growth of Bi2O3 nanoparticles constructed a "sandwich" configuration of a "double" S-shaped heterostructure. By precisely controlling the thickness of the TiO2{101} crystal plane, a synergistic enhancement effect of the electric field at the two interfaces was achieved, thereby constructing an efficient stepped charge transport channel, which significantly improved the spatial separation efficiency and directional migration capability of photogenerated carriers.

[0047] (iv) The TiO2{101} / Na prepared by this invention + Bi₂O₃ double S-type heterojunction nanosheets can be applied to photocatalytic hydrogen production and / or tetracycline degradation, compared to randomly assembled TiO₂ / Na₂... + Bi₂O₃ nanosheets exhibit significantly enhanced photocatalytic water splitting for hydrogen production in a system using triethanolamine as a sacrificial agent. Furthermore, in a reaction system using tetracycline as a hole sacrificial agent, this material can synergistically achieve efficient hydrogen production and tetracycline degradation, demonstrating excellent bifunctional photocatalytic activity. Attached Figure Description

[0048] Figure 1 The TiO2{101} / Na prepared in Example 1 of this invention + Transmission electron microscope image of Bi2O3 double S-type heterojunction nanosheets; Figure 2 The TiO2{101} / Na prepared in Example 1 of this invention +Selected area electron diffraction pattern of Bi2O3 double S-type heterojunction nanosheets; Figure 3 TiO2 / Na prepared for Comparative Example 1 + Transmission electron microscope image of Bi2O3 nanosheets; Figure 4 The TiO2{101} / Na prepared in Example 1 of this invention + X-ray diffraction pattern of Bi2O3 double S-type heterojunction nanosheets; Figure 5 The TiO2{101} / Na prepared in Example 1 of this invention + Performance curve of photocatalytic water splitting for hydrogen production from Bi2O3 double S-type heterojunction nanosheets; Figure 6 The TiO2 / Na prepared for Comparative Example 1 of this invention + -Performance curve of photocatalytic water splitting for hydrogen production from Bi2O3 nanosheets; Figure 7 The TiO2{101} / Na prepared in Example 1 of this invention + -Performance curves of photocatalytic tetracycline degradation and simultaneous hydrogen evolution of Bi2O3 double S-type heterojunction nanosheets; Figure 8 The TiO2 / Na prepared for Comparative Example 1 of this invention + -Performance curves of photocatalytic tetracycline degradation and simultaneous hydrogen evolution of Bi2O3 nanosheets. Detailed Implementation

[0049] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials used in the following embodiments can be obtained from conventional commercial channels or prepared and isolated through simple synthesis; unless otherwise specified, the processes employed are conventional processes in the art.

[0050] Example 1 This embodiment provides a TiO2{101} / Na + The preparation method of Bi₂O₃ double S-type heterojunction nanosheets is as follows: S1. Weigh 3 mL of tetrabutyl titanate and dissolve it in 8 mL of ethanol. Stir magnetically until a clear solution is obtained. Add 0.8 mL of hydrofluoric acid to the above solution and stir magnetically to form a homogeneous solution. S2. The homogeneous solution of S1 was placed into a 20 mL reaction vessel and crystallized at 180 °C for 12 h. After naturally cooling to room temperature, the white powder was collected by centrifugation, washed several times with ethanol and deionized water, and dried at 60 °C for later use to obtain TiO2 nanosheets. S3. Weigh 50 mg of the white powder synthesized in S2 and dissolve it in 30 mL of water. Sonicate the solution for 30 min to disperse it evenly and then stir it magnetically to form a homogeneous solution. S4. Weigh 14.58 mg of NaBiO3 and disperse it in the homogeneous solution of S3. Irradiate the solution under a UV-Vis lamp for 120 min. The UV-Vis lamp intensity is 400 mW / cm². 2 The wavelength was 400 nm (this parameter was also used in the following examples and comparative examples). The powder was collected by centrifugation, washed with ethanol and deionized water, and dried in air at 80°C to obtain powdered TiO2{101} / Na. + -Bi2O3 nanosheets.

[0051] Example 2 This embodiment provides a TiO2{101} / Na + The preparation method of Bi₂O₃ double S-type heterojunction nanosheets is as follows: S1. Weigh 3 mL of tetrabutyl titanate and dissolve it in 8 mL of ethanol. Stir magnetically until a clear solution is obtained. Add 0.8 mL of hydrofluoric acid to the above solution and stir magnetically to form a homogeneous solution. S2. The homogeneous solution of S1 was placed into a 20 mL reaction vessel and crystallized at 160 °C for 14 h. After naturally cooling to room temperature, the white powder was collected by centrifugation, washed several times with ethanol and deionized water, and dried at 60 °C for later use to obtain TiO2 nanosheets. S3. Weigh 50 mg of the white powder synthesized in S2 and dissolve it in 30 mL of water. Sonicate the solution for 30 min to disperse it evenly and then stir it magnetically to form a homogeneous solution. S4. Weigh 17.5 mg of NaBiO3 and disperse it in the homogeneous solution of S3. Irradiate it under a UV-vis lamp for 180 min, centrifuge to collect the powder, wash it with ethanol and deionized water, and dry it in air at 80°C to obtain the powder.

[0052] Example 3 This embodiment provides a TiO2{101} / Na + The preparation method of Bi₂O₃ double S-type heterojunction nanosheets is as follows: S1. Weigh 1 mL of titanium tetrachloride and dissolve it in 8 mL of ethanol. Stir magnetically until a clear solution is obtained. Add 0.8 mL of hydrofluoric acid to the above solution and stir magnetically to form a homogeneous solution. S2. The homogeneous solution of S1 was placed into a 20 mL reaction vessel and crystallized at 160 °C for 12 h. After naturally cooling to room temperature, the white powder was collected by centrifugation, washed several times with ethanol and deionized water, and dried at 60 °C for later use to obtain TiO2 nanosheets. S3. Weigh 50 mg of the white powder synthesized in S2 and dissolve it in 30 mL of water. Sonicate the solution for 30 min to disperse it evenly and then stir it magnetically to form a homogeneous solution. S4. Weigh 10.94 mg of NaBiO3 and disperse it in the homogeneous solution of S3. Irradiate it under a UV-vis lamp for 150 min, centrifuge to collect the powder, wash it with ethanol and deionized water, and dry it in air at 80°C to obtain the powder.

[0053] Comparative Example 1 This comparative example provides a TiO2 / Na + The preparation method of the -Bi2O3 composite material is as follows: S1. Weigh 3 mL of tetrabutyl titanate and dissolve it in 8 mL of ethanol. Stir magnetically until a clear solution is obtained. Add 0.8 mL of hydrofluoric acid to the above solution and stir magnetically to form a homogeneous solution. S2. The homogeneous solution of S1 was placed into a 20 mL reaction vessel and crystallized at 180 °C for 12 h. After naturally cooling to room temperature, the white powder was collected by centrifugation, washed several times with ethanol and deionized water, and dried at 60 °C for later use to obtain TiO2 nanosheets. S3. Weigh 50 mg of the white powder synthesized in S2 and dissolve it in 30 mL of water. Sonicate the solution for 30 min to disperse it evenly and then stir it magnetically to form a homogeneous solution. S4. Weigh 14.58 mg NaBiO3 and 13.12 mg Na2SO3 and disperse them in the homogeneous solution of S3. Transfer the resulting mixture to a water bath at 80°C and stir continuously for 2 h. Evaporate the moisture in air at 100°C until dry to obtain a powder.

[0054] Characterization of heterojunction materials 1. Characterization by transmission electron microscopy (TEM) The morphology and structure of the samples synthesized in Example 1 and Comparative Example 1 of this invention were analyzed using a JEOL JEM-2100 transmission electron microscope with an operating voltage of 300 kV. Figure 1 The image shows a transmission electron microscope (TEM) image of Example 1, with Na... + Bi₂O₃ nanoparticles are uniformly distributed at the edges of TiO₂ nanosheets, i.e., the TiO₂{101} plane. The size of the TiO₂ nanosheets is 20~35 nm, and Na₂O₃ nanoparticles are uniformly distributed at the edges of the TiO₂ nanosheets, i.e., the TiO₂{101} plane. + The size of Bi₂O₃ nanoparticles is 1~2 nm. Figure 2 The selected area electron diffraction pattern is shown, and the diffraction rings correspond to TiO2(101) / Na. + -Bi2O3(111), TiO2(004), TiO2(200) and TiO2(105) crystal planes, proving Na+ Bi2O3 was successfully grown on the TiO2 surface. Figure 3 The image shows a transmission electron microscope (TEM) image of Comparative Example 1, as shown in the figure. Na + Bi₂O₃ nanoparticles are uniformly distributed on all surfaces of TiO₂ nanosheets. The size of the TiO₂ nanosheets is 20–35 nm. + The size of the Bi2O3 nanoparticles is 1~2 nm.

[0055] 2. X-ray diffraction (XRD) characterization The sample prepared in Example 1 of this invention was characterized by XRD phase analysis using a D8 Advance X-ray diffractometer. The results are as follows: Figure 4 As shown in the figure, the XRD pattern reveals characteristic diffraction peaks of both anatase TiO2 and cubic δ-Bi2O3 phases in the sample. Notably, compared to the standard δ-Bi2O3 diffraction card (JCPDS No. 27-0052), the diffraction peaks of the δ-Bi2O3 phase in the sample are shifted towards lower angles. This shift can be attributed to Na... + The effect of doping on the lattice structure of Bi₂O₃: Na + The introduction of oxygen vacancies promotes their formation through a charge compensation mechanism, leading to lattice expansion. According to Bragg's equation (2dsinθ = nλ), an increase in the interplanar spacing d will cause a decrease in the diffraction angle θ, resulting in a shift of the diffraction peak position to a lower angle.

[0056] Photocatalytic activity test 1. Experimental Methods (1) Photocatalytic hydrogen production: The photocatalytic hydrogen production experiment was carried out in a 35 mL quartz reactor. Approximately 5 mg of the sample from Example 1 or Comparative Example 1 of this invention was suspended in 10 mL of an aqueous solution containing 20 vol.% triethanolamine as a sacrificial agent. The mixture was sealed in the quartz reactor with a rubber stopper and purged with argon gas for 10 min with continuous stirring to remove residual air. Subsequently, the reactor was exposed to UV-vis light (300 W xenon lamp, PLS-SXE300D, 400 mW cm⁻¹). -2 The quartz reactor was placed in a water tank connected to a reflux condenser to maintain the catalytic reaction temperature. The generated hydrogen gas was periodically analyzed every 30 minutes by a gas chromatograph (GC) equipped with a thermal conductivity detector (TCD) (Beijing Beifen Ruili Analytical Instrument SP-3420A).

[0057] (2) Photocatalytic degradation and simultaneous hydrogen evolution: Approximately 5 mg of sample from Examples 1-3 or Comparative Example 1 of this invention was dispersed in 20 mL of tetracycline aqueous solution (concentration of tetracycline aqueous solution was 20 mg / L), ultrasonically dispersed, and injected into the reaction system after a uniform dispersion was formed. High-purity argon gas was continuously introduced for 10 min under magnetic stirring to fully remove air from the system. The reaction system was then stirred in the dark for 30 min to ensure sufficient adsorption of tetracycline by the catalyst and to reach adsorption-desorption equilibrium. Subsequently, UV-vis light irradiation (300 W xenon lamp, PLS-SXE300D, 400 mW·cm⁻¹) was applied. -2 Throughout the reaction, the reactor was placed in a circulating water condenser to ensure that the reaction system temperature remained constant. During the reaction, the generated hydrogen gas was measured using a gas chromatograph equipped with a thermal conductivity detector (TCD), and the reaction solution was collected, filtered through a 0.45 μm organic filter membrane, and the tetracycline concentration was measured using a UV-Vis spectrophotometer.

[0058] 2. Results of photocatalytic hydrogen production experiments (1) The change of product gas with light exposure time was measured using a gas chromatograph equipped with a TCD detector. Figure 5 The TiO2{101} / Na prepared in Example 1 of this invention + The performance curves of photocatalytic water splitting for hydrogen production from Bi2O3 double S-type heterojunction nanosheets are shown in Table 1. Specific data for Examples 1-3 are shown in Table 1.

[0059] Table 1. Gas yield at different times during photocatalytic water splitting reaction

[0060] from Figure 5 As shown in Table 1, the TiO2{101} / Na prepared in this invention... + The rate of hydrogen production from water splitting using the Bi₂O₃ double S-type heterojunction nanosheet photocatalyst is ~63.2 μmol·h⁻¹. 1 .

[0061] (2) The TiO2 / Na prepared in Comparative Example 1 + - Replace the TiO2{101} / Na obtained in Example 1 of Application Example 1 with Bi2O3 nanosheets. + -Bi₂O₃ nanosheets, otherwise the same as in Application Example 1. The change in product gas with illumination time was measured using a gas chromatograph equipped with a TCD detector; the results are shown in [Figure 1]. Figure 6 And Table 2.

[0062] Table 2 Gas yield at different times in the photocatalytic water splitting reaction of the comparative materials

[0063] Depend on Figure 6 As shown in Table 2, TiO2 / Na + Bi₂O₃ nanosheets, under photocatalysis, can produce hydrogen by splitting water at a rate of ~9.0 μmol / h. 1 In other words, the TiO2{101} / Na prepared in this invention... + The hydrogen production rate of Bi₂O₃ double S-type heterojunction nanosheets is TiO₂ / Na + -Bi2O3 nanosheets have a hydrogen production rate that is ~7 times higher.

[0064] 3. Photocatalytic degradation and simultaneous hydrogen evolution (1) The generated hydrogen gas was measured by a gas chromatograph equipped with a thermal conductivity detector (TCD). At the same time, the reaction solution was collected, filtered through a 0.45 μm organic filter membrane, and the tetracycline concentration was measured by a UV-Vis spectrophotometer. Figure 7 The TiO2{101} / Na prepared in Example 1 of this invention + The performance curves of photocatalytic tetracycline degradation and simultaneous hydrogen evolution of Bi2O3 double S-type heterojunction nanosheets are shown in Table 3. The specific data corresponding to Examples 1-3 are shown in Table 3.

[0065] Table 3. Synergistic gas yield and tetracycline degradation rate at different photocatalytic times

[0066] from Figure 7 As shown in Table 3, the TiO2{101} / Na prepared in this invention... + Bi₂O₃ double S-type heterojunction nanosheets synergistically decompose water to produce hydrogen and degrade tetracycline under photocatalysis. When the reaction proceeded for 120 min, the hydrogen yield was ~2.90 mmol g. 1 The degradation rate of TC reached 98.1%.

[0067] (2) The TiO2 / Na prepared in Comparative Example 1 + - Replace the TiO2{101} / Na obtained in Example 1 of Application Example 1 with Bi2O3 nanosheets. + -Bi₂O₃ nanosheets, otherwise the same as in Application Example 1. The generated hydrogen gas was measured using a gas chromatograph equipped with a thermal conductivity detector (TCD). Simultaneously, the reaction solution was collected, filtered through a 0.45 μm organic filter membrane, and the tetracycline concentration was determined using a UV-Vis spectrophotometer. The results are shown in [Figure number missing]. Figure 8 And Table 4.

[0068] Table 4. Gas yield and tetracycline degradation rate at different photocatalytic times

[0069] Depend on Figure 8 As shown in Table 4, TiO2 / Na + Bi₂O₃ nanosheets synergistically decompose water to produce hydrogen and degrade tetracycline under photocatalysis. When the reaction proceeded for 120 min, the hydrogen yield was ~1.84 mmol g. 1 The degradation rate of TC reached 62.5%. That is to say, compared with TiO2 / Na... + Compared to Bi₂O₃ nanosheets, the TiO₂{101} / Na₂ prepared in this invention... + -Bi2O3 double S-type heterojunction nanosheets showed a simultaneous 1.6-fold increase in activity for water splitting to produce hydrogen and for tetracycline degradation within 120 min.

[0070] In summary, this invention addresses the problems of low carrier separation efficiency, single transport path, and complex ternary heterojunction structure in traditional photocatalytic systems during synergistic hydrogen production and pollutant degradation. It proposes an innovative strategy based on crystal plane engineering and bandgap modulation, successfully designing and preparing a TiO2{101} / Na system with a double S-shaped heterojunction structure in a binary composite system. + -Bi₂O₃ nanosheets. This material fully utilizes the directional growth characteristics of the {101} crystal plane, combined with Na₂O₃... + Doping optimizes the band structure of Bi2O3, creating a stepped charge transport channel that significantly enhances the separation and migration efficiency of photogenerated carriers. Experimental results show that this material exhibits excellent catalytic activity in both photocatalytic water splitting for hydrogen production and synergistic reactions with tetracycline degradation, providing a new material design approach and feasible technical pathway for realizing efficient and concise bifunctional photocatalytic systems.

[0071] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A double S-shaped heterojunction composite material, characterized in that, This includes TiO2 nanosheets, the surface of which is loaded with Na. + -Bi2O3 nanoparticles; the Na + -Bi₂O₃ nanoparticles are doped with Na + Bi2O3 nanoparticles.

2. The double S-shaped heterojunction composite material according to claim 1, characterized in that, The TiO2 nanosheets are TiO2 nanosheets with exposed {001} and {101} crystal planes; the Na + -Bi2O3 nanoparticles are loaded on the {101} crystal plane of TiO2 nanosheets.

3. The double S-shaped heterojunction composite material according to claim 1, characterized in that, The Na + The particle size of the Bi2O3 nanoparticles is 1~10 nm.

4. The method for preparing the double S-shaped heterojunction composite material according to any one of claims 1-3, characterized in that, Includes the following steps: TiO2 nanosheets and NaBiO3 were added to water and reacted under ultraviolet-visible light irradiation; the solid product was collected after the reaction and dried to obtain the double S-type heterojunction composite material.

5. The method for preparing the double S-shaped heterojunction composite material according to claim 4, characterized in that, The molar ratio of Ti in the TiO2 nanosheets to Bi in NaBiO3 is (8~20):

1.

6. The method for preparing the double S-shaped heterojunction composite material according to claim 4, characterized in that, The wavelength of the ultraviolet-visible light is 320-780 nm.

7. The method for preparing the double S-shaped heterojunction composite material according to claim 4, characterized in that, The reaction time is 60-200 min.

8. The method for preparing the double S-shaped heterojunction composite material according to claim 4, characterized in that, The preparation method of the TiO2 nanosheets includes the following steps: A titanium source was added to a hydrofluoric acid solution and mixed and stirred to obtain a reaction precursor. The reaction precursor was then transferred to a reaction vessel for a solvothermal reaction to obtain TiO2 nanosheets.

9. The application of the double S-shaped heterojunction composite material according to any one of claims 1-3 in photocatalytic water splitting for hydrogen production.

10. The use of the double S-shaped heterojunction composite material according to any one of claims 1-3 in the degradation of tetracycline antibiotics.

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