Bismuth oxybromide modified strontium titanate photocatalytic material and preparation method thereof

Abstract

The invention provides a bismuth oxybromide modified strontium titanate photocatalytic material and a preparation method thereof. According to the method, the synergistic effect of bromide and bismuth salt is adopted, through complexing of hydroxyl (-OH) and Bi < 3 + > ions, the nucleation rate of BiOBr is successfully controlled, particle aggregation is inhibited, and finally the photocatalytic composite material with the flower-like microsphere structure is formed. By constructing the SrTiO3 / BiOBr heterojunction, the forbidden band width of the composite material is obviously reduced, the visible light absorption range is obviously widened, the separation efficiency of photon-generated carriers is improved, and the photocatalytic performance is promoted to be enhanced. The composite material shows remarkable photocatalytic activity under visible light, formaldehyde in air can be efficiently removed, and the removal rate is 70% or above. The preparation process is simple and environment-friendly, and has a wide application prospect, especially in the fields of air purification and water treatment.

Description

Technical Field

[0001] The present invention relates to the field of photocatalytic materials, and in particular to a method for preparing a bismuth oxybromide-modified strontium titanate photocatalytic material. This material is primarily used in the field of environmental protection, particularly in indoor air purification and wastewater treatment, and can efficiently degrade harmful gases such as formaldehyde. Background Art

[0002] With the acceleration of industrialization and urbanization, organic pollutants in water and air, particularly volatile organic compounds (VOCs) like formaldehyde, have become a major issue in environmental governance that requires urgent attention. Traditional pollutant treatment methods, such as adsorption, chemical degradation, and biodegradation, suffer from low efficiency, complex operations, and the risk of secondary pollution, making them unable to meet the increasingly stringent environmental governance needs.

[0003] Semiconductor photocatalysis, particularly redox reactions driven by visible light, has become a research hotspot in recent years due to its high efficiency and environmental friendliness. Strontium titanate (SrTiO3), a typical perovskite semiconductor material, has great potential for application in photocatalysis due to its stable crystal structure, moderate band gap (approximately 3.2 eV), and strong redox ability. However, due to its primarily UV absorption range and high recombination rate of photogenerated carriers, its photocatalytic efficiency under visible light conditions is low, limiting its practical application.

[0004] In recent years, scientists have attempted to improve the photocatalytic properties of strontium titanate through methods such as doping, alloying, and metal or non-metal modification. Bismuth oxybromide (BiOBr) exhibits significant advantages in photocatalysis due to its unique layered structure, moderate band gap (2.6-2.9 eV), and strong ability to separate photogenerated carriers. BiOBr not only broadens the light absorption range but also significantly enhances photocatalytic performance by forming a heterojunction with strontium titanate.

[0005] To meet this challenge, the present invention proposes a bismuth oxybromide modified strontium titanate photocatalytic material and a preparation method thereof. Summary of the Invention

[0006] In view of this, the present invention provides a bismuth oxybromide modified strontium titanate photocatalytic material and a preparation method thereof. The material has excellent photocatalytic performance, especially under visible light irradiation, and can effectively degrade organic pollutants such as formaldehyde. Its photocatalytic efficiency is stably maintained at above 70% in multiple cycle experiments, showing strong anti-attenuation performance, so as to solve or alleviate the technical problems existing in the prior art and at least provide a beneficial option.

[0007] The technical solution of the embodiment of the present invention is achieved as follows:

[0008] In a first aspect, the present invention provides a bismuth oxybromide modified strontium titanate photocatalytic material, comprising a mixture of the following components by weight: 0.1% to 5% strontium titanate, 0.1% to 5% bismuth salt, 80% to 95% solvent one, 5% to 10% solvent two, and 1% to 5% bromide.

[0009] In the above-mentioned bismuth oxybromide modified strontium titanate photocatalytic material, preferably, the strontium titanate, bismuth salt and bromide are all analytically pure reagents.

[0010] In the above-mentioned bismuth oxybromide modified strontium titanate photocatalytic material, preferably, the bismuth salt is one or more of Bi(NO3)3·5H2O and BiCl3 soluble bismuth salts.

[0011] In the above-mentioned bismuth oxybromide modified strontium titanate photocatalytic material, preferably, the bromide is a soluble bromide.

[0012] In the above-mentioned bismuth oxybromide modified strontium titanate photocatalytic material, preferably, the first solvent is a mixture of ethylene glycol and water.

[0013] The above-mentioned bismuth oxybromide modified strontium titanate photocatalytic material is preferably: the second solvent is a high boiling point alcohol solvent

[0014] A second aspect: A method for forming a bismuth oxybromide modified strontium titanate photocatalytic material, comprising the following steps:

[0015] Step 1: uniformly disperse strontium titanate (SrTiO3) and bismuth salt (such as Bi(NO3)3·5H2O) in solvent 1 (a mixture of ethylene glycol and water) and stir at high speed for 10 to 15 minutes to form suspension A;

[0016] Step 2: Add bromide (such as KBr) to the solvent di(ethylene glycol) and treat with ultrasound for 30 minutes to ensure that the bromide is completely dissolved to form solution B;

[0017] Step 3: Add suspension A to the reactor, start stirring and heat in an oil bath to 120°C. After constant temperature, slowly add solution B dropwise. The reaction time is 4 to 6 hours.

[0018] Step 4: After the reaction is completed, the precipitate is washed with deionized water and anhydrous ethanol several times, and dried in a forced air drying oven at 60° C. for 12 hours.

[0019] The embodiment of the present invention adopts the above technical solution, which has the following advantages:

[0020] The composite material of the present invention can effectively degrade formaldehyde in the air under visible light irradiation, with a formaldehyde removal rate of more than 70%, and has strong stability;

[0021] By slowing down the bismuth ion precipitation reaction through hydroxyl complexation, the crystal morphology of BiOBr was successfully controlled, achieving high dispersion and uniformity; the constructed Z-type heterojunction promoted carrier separation, significantly reduced the electron-hole recombination rate, and improved photocatalytic activity.

[0022] Bismuth oxybromide reacts with bismuth ions (Bi 3 +) to form a stable complex, slowing down the Bi 3 + with bromide ion (Br - This process effectively controls the nucleation rate of BiOBr and inhibits particle agglomeration, resulting in the formation of a flower-like microsphere structure in the final product.

[0023] The combination of BiOBr and SrTiO3 forms a Z-type heterojunction (BiOBr / SrTiO3), which can effectively promote the separation of photogenerated carriers, reduce the recombination rate, and thus improve the photocatalytic efficiency;

[0024] Since BiOBr has a wide visible light absorption range, it can enable the modified SrTiO3 to exhibit significant photocatalytic performance under visible light, especially in the degradation of formaldehyde.

[0025] The above summary is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features of the present invention will be readily apparent by reference to the accompanying drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0027] Figure 1 This is a flow chart of the preparation method of the bismuth oxybromide modified strontium titanate photocatalytic material of the present invention;

[0028] Figure 2 The SEM images of the blank sample SrTiO3 and the example sample of the present invention are as follows;

[0029] Figure 3 This is the EDS and corresponding element surface scan of Example 1 of the present invention. DETAILED DESCRIPTION

[0030] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be considered as illustrative in nature and not restrictive.

[0031] The following is combined with Figure 1 The embodiments of the present invention are described in detail.

[0032] A method for preparing a bismuth oxybromide modified strontium titanate photocatalytic material:

[0033] The preparation methods in the examples are all the same, and the specific process is as follows:

[0034] Step 1) uniformly dispersing strontium titanate and bismuth salt in solvent 1 and stirring at high speed for 10-15 minutes to form suspension A;

[0035] Step 2) adding the bromide to solvent 2 and sonicating for 30 min to dissolve the bromide to form solution B;

[0036] Step 3) Suspension A was added to the reactor, stirred, and heated in an oil bath to 120°C. After the temperature was constant, solution B was slowly added dropwise while stirring. The reaction was continued for 5 hours and then cooled.

[0037] Step 4) The precipitate was washed with deionized water and anhydrous ethanol several times and then dried in a forced air drying oven at 60° C. for 12 h.

[0038] Specifically:

[0039] 1. Raw material preparation and dispersion process:

[0040] First, high-purity strontium titanate (SrTiO3) and a bismuth salt (such as Bi(NO3)3·5H2O) are selected as the primary active components of the reaction. SrTiO3, due to its stable perovskite structure and excellent chemical and thermal stability, is the primary photocatalyst material in this system. The introduction of the bismuth salt provides a bismuth source for the formation of bismuth oxybromide (BiOBr).

[0041] Strontium titanate and bismuth salt are added to solvent 1 according to the designed weight ratio (see the embodiment for details). Solvent 1 is a mixed solvent of ethylene glycol and deionized water with a volume ratio of about 9:1. The choice of ethylene glycol is mainly based on its good solubility and high boiling point, which is conducive to regulating the reaction temperature and particle nucleation growth process. The hydroxyl (-OH) functional group of ethylene glycol can also react with Bi 3 + ions form a coordination complex, slowing down their interaction with Br - The reaction rate is reduced to prevent the excessive nucleation and particle agglomeration of BiOBr.

[0042] Under high-speed stirring conditions, strontium titanate and bismuth salt are evenly dispersed in the solvent and stirred continuously for 10-15 minutes to ensure that the two are fully mixed to form a stable suspension A. The key to this step is to achieve uniform distribution at the nanoscale, which promotes the subsequent uniform coating of bismuth oxybromide on the strontium titanate surface and the construction of a heterojunction interface.

[0043] 2. Preparation of bromide solution:

[0044] Bromide is selected from soluble salts such as KBr or NaBr to provide Br - Ion source. Add the designed amount of bromide to solvent 2, which is generally pure ethylene glycol or other high-boiling-point alcohol solvents.

[0045] To promote the complete dissolution and uniform dispersion of the bromide, ultrasonic treatment was used for 30 minutes. Ultrasonication can produce a strong cavitation effect, breaking up aggregates in the solution, increasing the dissolution rate and uniformity of the bromide, and ensuring the smooth progress of subsequent reactions.

[0046] After ultrasonic treatment, a uniform bromide solution B is obtained. - The ion concentration is stable, and the solvent environment is conducive to its interaction with Bi in suspension A. 3 + Slow reaction, controlling the nucleation and growth process of BiOBr.

[0047] 3. Preparation of composite reaction in reactor:

[0048] Suspension A was transferred to a sealed reactor, mechanically stirred, and the system temperature was raised to and maintained at 120°C using an oil bath. This temperature was kept within a relatively high range to ensure thermodynamic activity while preventing excessive particle growth and agglomeration due to high temperatures.

[0049] Under constant temperature conditions, slowly add solution B while stirring. Slow addition ensures that Bi 3 + and Br - The uniformity and controllability of the reaction can prevent the formation of irregular particles caused by local oversaturation. During the reaction, the hydroxyl groups of ethylene glycol in the solvent react with Bi 3 + formed a complex, which significantly delayed the nucleation rate of BiOBr and promoted the uniform deposition of BiOBr on the surface of strontium titanate in the form of flower-like microspheres, forming a compact heterojunction structure.

[0050] The reaction is maintained for 4 to 6 hours to ensure that the reaction is fully completed and a stable and structurally intact bismuth oxybromide-modified strontium titanate composite material is formed. After the reaction is completed, the system is naturally cooled to room temperature.

[0051] 4. Product washing and drying process:

[0052] After cooling, the precipitate is collected by centrifugation or filtration. To remove residual inorganic salts, impurities, and reaction byproducts, it is washed multiple times with alternating deionized water and anhydrous ethanol. Deionized water removes water-soluble impurities, while anhydrous ethanol helps remove organic residues and promotes dispersion between particles, preventing agglomeration.

[0053] The key to the washing step is to ensure the purity of the final product and avoid affecting its photocatalytic activity and structural integrity.

[0054] After washing, the product was placed in a forced air drying oven, the temperature was controlled at 60° C., and the drying time was 12 hours to fully remove the residual solvent and moisture to obtain a dry and uniform bismuth oxybromide modified strontium titanate photocatalytic material.

[0055] The samples in the examples were subjected to XRD, SET, and formaldehyde degradation tests in sequence.

[0056] Example 1

[0057] A bismuth oxybromide modified strontium titanate photocatalytic material comprises the following components by weight: 1% strontium titanate, 0.2% bismuth salt, 88.6% solvent 1, 10% solvent 2 and 0.2% bromide.

[0058] Dissolve pure strontium titanate powder in ethanol and stir evenly.

[0059] Barium bromide and bismuth nitrate dissolved in ethanol were added dropwise with continued stirring.

[0060] The solution is transferred to an autoclave, water is added and a solvothermal reaction is carried out at a certain temperature (eg, 180° C.) for 12 hours.

[0061] After the reaction is completed, the product is filtered and washed to obtain a composite material.

[0062] Finally, it was dried at 60°C to obtain the final composite strontium titanate and bismuth oxybromide material.

[0063] Material characterization:

[0064] XRD analysis: The crystal structure of the composite material was confirmed by X-ray diffraction analysis, which showed that a heterojunction structure was formed between strontium titanate and bismuth oxybromide, and that the crystal lattices of the two did not change significantly, maintaining the original crystal structure.

[0065] SEM analysis: Scanning electron microscope (SEM) images show that the composite material presents a flower-like microsphere structure, and the BiOBr layer is evenly distributed on the surface of the strontium titanate particles. This structure can effectively increase the specific surface area and improve the activity of the photocatalytic reaction.

[0066] This ratio ensures that bismuth salt and bromide participate in the reaction at low concentrations, facilitating the formation of small and evenly distributed BiOBr microspheres, effectively modifying strontium titanate. Photocatalytic testing showed that the prepared material achieved a 77% formaldehyde degradation rate under visible light irradiation, with excellent and stable performance over multiple cycles.

[0067] Example 2

[0068] A bismuth oxybromide modified strontium titanate photocatalytic material comprises the following components by weight: 1% strontium titanate, 0.4% bismuth salt, 88.2% solvent 1, 10% solvent 2 and 0.4% bromide.

[0069] A formaldehyde degradation experiment was conducted on the prepared strontium titanate and bismuth oxybromide composite material. The specific steps are as follows:

[0070] Formaldehyde degradation experimental setup:

[0071] Laboratory simulation environment: a certain amount of formaldehyde solution is added into a closed glass reactor.

[0072] Reaction conditions: Place the reactor under visible light to ensure that the reaction process proceeds in the visible light region.

[0073] Reaction time: Samples were taken at regular intervals and changes in formaldehyde concentration were detected using gas chromatography.

[0074] Experimental results:

[0075] Degradation Efficiency: According to experimental results, the formaldehyde degradation rate of the pure strontium titanate sample under visible light was 14%, while the formaldehyde degradation rate of the composite material was as high as 77%. The composite material of Example 1 achieved a formaldehyde degradation rate of 77% in the first experiment and remained above 70% throughout the four cycles of testing, demonstrating its strong stability and repeatability.

[0076]

[0077] Compared with Example 1, the bismuth salt and bromide content was increased to promote BiOBr nucleation, but the excessive amount may cause slight particle agglomeration, and the photocatalytic activity was slightly reduced. However, it was still better than that of pure strontium titanate material, with a formaldehyde degradation rate of 68%.

[0078] Example 3

[0079] A bismuth oxybromide modified strontium titanate photocatalytic material comprises the following components by weight: 1% strontium titanate, 0.6% bismuth salt, 87.8% solvent 1, 10% solvent 2 and 0.6% bromide.

[0080] Further increasing the Bi and Br content, it was observed that the particle size of bismuth oxybromide increased and agglomeration was obvious, resulting in the coverage of some active sites and a decrease in photocatalytic efficiency. The formaldehyde degradation rate was 67%, but the cycle stability remained good.

[0081] Example 4

[0082] A bismuth oxybromide-modified strontium titanate photocatalytic material, the raw materials of which contain the following components by weight:

[0083] Bismuth salt 1%, solvent 1 88%, solvent 2 10% and bromide 1%;

[0084] In this example, pure bismuth oxybromide was prepared by reacting a pure bismuth salt, solvent 1, solvent 2, and bromide. This material is primarily composed of stacked rod-like structures, forming a rosette-like structure. XRD and SEM characterization results indicate that the prepared bismuth oxybromide material exhibits a favorable crystal structure and surface morphology.

[0085] XRD and SEM analysis

[0086] XRD Analysis: The crystal structures of all example materials (including pure strontium titanate, bismuth oxybromide-modified strontium titanate, and bismuth oxybromide alone) were confirmed by X-ray diffraction analysis. The pure strontium titanate sample exhibited irregular spherical particles, while the bismuth oxybromide-modified strontium titanate material exhibited a clear Z-type heterojunction structure, demonstrating its stable crystal structure and excellent photocatalytic performance.

[0087] SEM images show that bismuth oxybromide alone exhibits relatively regular rod-shaped particles. After the solvent's hydroxyl groups react, the bismuth oxybromide material forms a flower-like microsphere structure, which contrasts sharply with the particle structure of pure strontium titanate. This structure effectively inhibits particle aggregation, increases the material's specific surface area, and promotes the occurrence of photocatalytic reactions.

[0088] Formaldehyde degradation test:

[0089] The formaldehyde degradation performance of each sample was tested, and the results are shown in Table 1 below:

[0090]

[0091] Table 1: Formaldehyde degradation rate table of examples

[0092] Example 1 shows the highest formaldehyde degradation rate, reaching 77%. Even after four cycles of testing, the formaldehyde degradation rate remains above 70%, indicating that the material has excellent photocatalytic performance under visible light and good stability.

[0093] Cycle test:

[0094] Table 2 below shows the formaldehyde degradation effect of Example 1 over four cycles, with almost no degradation. This result demonstrates the high stability of the material and its long-term performance.

[0095] Number of cycles Cycle 1 Cycle 2 Cycle 3 Cycle 4

[0096] Formaldehyde purification rate 77% 75% 76% 75%

[0097] Table 2: Formaldehyde degradation rate of sample cycle test in Example 1

[0098] The material exhibits stable photocatalytic properties during use and has sustainable environmental benefits. It can stably degrade harmful substances in the air over a long period of time and improve indoor air quality.

[0099] Summary of experimental results:

[0100] The formaldehyde degradation efficiency of the bismuth oxybromide modified strontium titanate photocatalytic material under visible light is consistently above 70%, with the optimal value reaching 77%, demonstrating excellent photocatalytic performance.

[0101] Even after multiple cycle tests, the photocatalytic activity of the material did not significantly decay, demonstrating the long-term stability and reusability of the material in practical applications.

[0102] The preparation process of the photocatalytic material is simple and does not require complicated chemical treatment, thus meeting environmentally friendly requirements and being easy to promote and apply.

[0103] exist Figure 2 Medium purity strontium titanate presents irregular spherical particles, while bismuth oxybromide ( Figure 2 Example 4 shows a rosette-like structure formed by the accumulation of numerous rod-shaped bismuth oxybromide particles. During the bismuth oxybromide synthesis process, the hydroxyl groups in the alcoholic solution form a stable complex with Bi⁺⁺, slowing the rapid binding of Bi⁺⁺ with Br⁻⁻. This controls the nucleation rate of the bismuth oxybromide and inhibits particle aggregation, ultimately forming a flower-like microsphere structure.

[0104] Figure 3 EDS spectroscopy analysis of the bismuth oxybromide-modified strontium titanate photocatalytic material synthesized in Example 1 shows that the heterojunction is primarily composed of Sr, Ti, O, Bi, and Br, and the outline of bismuth oxybromide r is clearly visible within the composite material structure. Therefore, bismuth oxybromide-modified strontium titanate materials were successfully synthesized in Examples 1, 2, and 3.

[0105] In addition, by testing the formaldehyde removal rate of each sample in the liquid phase under visible light catalysis, according to Table 1, the best formaldehyde purification effect in Example 1 is 77%, and the formaldehyde degradation rate is above 70% after four consecutive tests without attenuation.

[0106] By combining bismuth oxybromide (BiOBr) and strontium titanate (SrTiO3), a Z-type heterojunction was formed, which greatly improved the photocatalytic efficiency and expanded the light response range of the material, especially under visible light.

[0107] The nucleation rate of BiOBr was controlled by the action of solvent hydroxyl groups, which effectively avoided particle agglomeration and successfully produced a flower-like microsphere structure, thereby increasing the specific surface area of ​​the photocatalyst and the number of reaction active sites.

[0108] The formaldehyde degradation rate remained stable during the cyclic test, proving the high stability of the material and its ability to meet long-term use requirements. The bismuth oxybromide-modified strontium titanate photocatalytic material has excellent visible light catalytic performance and can efficiently remove harmful substances such as formaldehyde from the air.

[0109] The preparation process is simple, low-cost and environmentally friendly, and is suitable for large-scale application in indoor air purification and other fields.

[0110] Comparative Example 1

[0111] Preparation conditions:

[0112] A bismuth oxybromide-modified strontium titanate photocatalytic material, the raw materials of which contain the following components by weight:

[0113] Material formula:

[0114] SrTiO3: 1%;

[0115] The rest was a mixture of deionized water and ethylene glycol (9:1);

[0116] Preparation process:

[0117] Dispersing SrTiO3 in a glycol / water mixed solvent;

[0118] Ultrasonic dispersion for 10 minutes;

[0119] No subsequent modification reaction;

[0120] Wash and dry (60℃ for 12h) to obtain powder.

[0121] Morphology: SEM shows irregular particle agglomeration with large grains;

[0122] XRD: Typical SrTiO3 peaks can be seen;

[0123] Formaldehyde removal rate (visible light, 60min): 14%;

[0124] Specifically, SrTiO3 has a stable lattice structure, but a high recombination rate of photogenerated carriers and almost no visible light response.

[0125] Comparative Example 2

[0126] Preparation conditions:

[0127] A bismuth oxybromide modified strontium titanate photocatalytic material, the raw materials of which contain the following components by weight: Material formula:

[0128] Bi(NO3)3·5H2O:1%,

[0129] KBr: 1%;

[0130] Ethylene glycol / water mixture + ethylene glycol;

[0131] Preparation process:

[0132] Dissolve Bi salt and KBr in corresponding solvents respectively;

[0133] React in an oil bath at 120°C for 5 h;

[0134] The product is obtained after washing and drying.

[0135] Test results:

[0136] Morphology: Flower-like microsphere structure is formed and evenly distributed;

[0137] XRD: typical diffraction peaks of BiOBr;

[0138] Formaldehyde removal rate: 34%;

[0139] Specifically:

[0140] BiOBr can respond to visible light, but its oxidation ability is weak, it is easily photocorroded, and the electron-hole recombination rate is still high.

[0141] Comparative Example 3:

[0142] Preparation conditions:

[0143] A bismuth oxybromide modified strontium titanate photocatalytic material, the raw materials of which contain the following components by weight: Material formula:

[0144] SrTiO3: 1%;

[0145] BiOBr: 1%;

[0146] Physical mixing was performed using mechanical ball milling;

[0147] Preparation process:

[0148] Prepare SrTiO3 and BiOBr separately;

[0149] Weigh the two materials in a ratio of 1:1 and then mix them by ball milling;

[0150] Use for testing after drying.

[0151] Test results:

[0152] Morphology: two phases are clearly separated;

[0153] XRD: SrTiO3 and BiOBr peaks overlap, with no shift or new peaks;

[0154] Formaldehyde degradation rate: 42%

[0155] Specifically:

[0156] Although the absorption range has been expanded, the performance improvement is limited due to the loose contact between the two materials at the interface, poor charge transfer, and failure to form an effective heterojunction.

[0157] Comparative Example 4:

[0158] Preparation conditions:

[0159] A bismuth oxybromide modified strontium titanate photocatalytic material, the raw materials of which contain the following components by weight: Material formula:

[0160] SrTiO3: 1%;

[0161] Bi(NO3)3·5H2O:0.4%;

[0162] KBr: 0.4%;

[0163] Deionized water was the only solvent;

[0164] Preparation process:

[0165] Same as the original process, but replacing ethylene glycol with pure water;

[0166] The reaction conditions remained consistent;

[0167] Test after washing and drying.

[0168] Test results:

[0169] Morphology: BiOBr particles are obviously agglomerated, without "roset" structure;

[0170] XRD: The peak width becomes wider, indicating low crystallinity;

[0171] Formaldehyde removal rate: 49%;

[0172] Specifically:

[0173] Lack of alcohol solution hydroxyl groups and Bi 3 + Complexation regulation causes the nucleation rate to lose control, which can easily lead to particle agglomeration and unclear heterogeneous interface, thereby inhibiting the composite effect and catalytic efficiency.

[0174]

[0175] Example 1 (the present invention) is superior to the above four comparison samples in terms of forming a flower-like microsphere structure, clear heterojunction, the appearance or displacement of new peaks shown in XRD, and a visible light degradation rate of 77%. It shows significant progress in morphology, crystal structure, light response ability and application effect, and has sufficient innovation and substantial effect.

[0176] Scanning electron microscopy (SEM) observations revealed that pure strontium titanate particles exhibited irregular spherical shapes with a wide size distribution, while bismuth oxybromide exhibited typical rod-like structures aggregated into rosette-like microspheres. The composite material exhibited distinct rosette-like microsphere morphology, with BiOBr uniformly coated on the surface of the strontium titanate particles.

[0177] Elemental distribution analysis (EDS) further confirmed the uniform distribution of Sr, Ti, O, Bi, and Br, indicating that bismuth oxybromide and strontium titanate were successfully composited, forming a close interface contact, which is conducive to the effective separation and transfer of charges.

[0178] The photocatalytic degradation test of formaldehyde solution was carried out using simulated visible light source. The results showed that the modified material was significantly better than pure strontium titanate, the formaldehyde removal rate was greatly improved, and the performance was stable in multiple cycles, indicating that the material has good photocatalytic activity and durability.

[0179] By rationally designing the solvent system and reaction conditions, and utilizing the hydroxyl functionality of alcohol solvents to effectively control the nucleation rate of BiOBr, a bismuth oxybromide-modified strontium titanate composite photocatalytic material with a flower-like microsphere structure was successfully obtained. This material combines good structural stability with remarkable photocatalytic performance, showing excellent application potential in environmental remediation, particularly in the degradation of formaldehyde pollution.

[0180] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various modifications and substitutions within the technical scope disclosed in the present invention, and such modifications and substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A bismuth oxybromide modified strontium titanate photocatalytic material, characterized in that: The invention comprises the following components mixed in weight percentage: 0.1% to 5% of strontium titanate, 0.1% to 5% of bismuth salt, 80% to 95% of solvent 1, 5% to 10% of solvent 2 and 1% to 5% of bromide.

2. The bismuth oxybromide modified strontium titanate photocatalytic material according to claim 1, characterized in that: The strontium titanate, bismuth salt and bromide are all analytically pure reagents.

3. The bismuth oxybromide modified strontium titanate photocatalytic material according to claim 1, characterized in that: The bismuth salt is one or more of Bi(NO3)3·5H2O and BiCl3 soluble bismuth salts.

4. The bismuth oxybromide modified strontium titanate photocatalytic material according to claim 1, characterized in that: The bromide is a soluble bromide.

5. The bismuth oxybromide modified strontium titanate photocatalytic material according to claim 1, characterized in that: The first solvent is a mixture of ethylene glycol and water.

6. The bismuth oxybromide modified strontium titanate photocatalytic material according to claim 1, characterized in that: The second solvent is a high boiling point alcohol solvent.

7. A method for preparing a bismuth oxybromide modified strontium titanate photocatalytic material according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: uniformly disperse strontium titanate and bismuth salt in solvent 1, and stir at high speed for 10 to 15 minutes to form suspension A; Step 2: Add the bromide to solvent 2 and dissolve it using ultrasonic treatment for 30 minutes to form solution B; Step 3: Add suspension A to the reactor, start stirring, heat in an oil bath, slowly add solution B dropwise after constant temperature, react for 4 to 6 hours, and finally cool; Step 4: Wash the precipitate with deionized water and anhydrous ethanol several times, and then dry it.

8. The method for forming the bismuth oxybromide modified strontium titanate photocatalytic material according to claim 6, wherein: The oil bath heating temperature is 100°C to 150°C.

9. The method for forming the bismuth oxybromide modified strontium titanate photocatalytic material according to claim 6, wherein: The washing method comprises washing with deionized water and anhydrous ethanol for several times.

10. The method for forming the bismuth oxybromide modified strontium titanate photocatalytic material according to claim 6, characterized in that: The drying operation is carried out in a forced air drying oven at 60 to 80° C. for 12 to 24 hours.

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