SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material, preparation method and application thereof
By dispersing a monolayer of Ti3C2-derived SrTiO3 on the surface of BiFeO3, a piezoelectric photocatalytic composite material of SrTiO3/BiFeO3 is formed. The polarization electric field of BiFeO3 is used to separate photogenerated electron-hole pairs, which solves the problem of severe recombination of photogenerated electron-hole pairs in SrTiO3 material and realizes a highly efficient photocatalytic water splitting reaction.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ANHUI UNIV
- Filing Date
- 2024-11-01
- Publication Date
- 2026-06-12
Smart Images
Figure CN119406418B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of piezoelectric photocatalysis technology, specifically to a SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material, its preparation method, and its application. Background Technology
[0002] With the increasing severity of global energy shortages and environmental pollution, solar energy, as a clean energy source, has attracted much attention due to its abundant resources and environmental friendliness. It can be directly converted into electricity or used to produce other green energy sources, such as hydrogen. Hydrogen energy, as an important component of the future global energy system, has advantages such as high calorific value, cleanliness, and abundant reserves. Photocatalytic water splitting produces H2 and O2 without relying on costly and environmentally polluting sacrificial agents, making it considered the most efficient and green way to utilize renewable energy.
[0003] The basic principle of photocatalysis is that under illumination, semiconductor photocatalytic materials absorb photons to generate free electrons and holes. Electron-hole pairs migrate to the material surface and undergo oxidation and reduction reactions with adsorbates, respectively. However, electron-hole pairs easily recombine in the bulk phase or on the surface during migration, and only a small fraction of charge carriers can escape the Coulomb forces and migrate to the semiconductor surface to participate in the photocatalytic reaction. Therefore, effectively improving the spatial separation of electron-hole pairs is one of the key problems that needs to be solved in photocatalysis technology.
[0004] Piezoelectric polarization can be coupled with photoexcitation and semiconductor properties, and the generation, separation, transport, and recombination of charge carriers can be effectively regulated through the polarization electric field. Under external stress, positive and negative polarization charges are formed on the catalyst surface. These positive and negative polarization charges are opposite in charge to the photogenerated electrons and holes. The polarization electric field generated by the directional migration of polarization charges can effectively promote the migration of photogenerated electron-hole pairs in opposite directions, thereby suppressing charge carrier recombination and greatly improving the separation efficiency of photogenerated charge carriers.
[0005] Many piezoelectric / ferroelectric materials, such as ZnO, BaTiO3, KNbO3, and lead zirconate titanate (PZT), have been used in the field of piezoelectric photocatalysis. Multiferrobismuth ferrite (BiFeO3) with perovskite structure is a prominent p-type semiconductor in solar drive applications. It has a rhombohedral twisted perovskite structure with R3c spatial groups, visible light absorption capability (narrow bandgap of 2.1–2.7 eV), is non-toxic, low cost, can spontaneously polarize, and can form a polarization electric field under periodic ultrasound to promote the separation of photogenerated carriers.
[0006] SrTiO3 is a highly active, stable, non-toxic, and low-cost semiconductor photocatalyst with high thermoelectric power, dielectric constant, and metallic conductivity, exhibiting good response to ultraviolet light. However, it suffers from severe photogenerated electron-hole recombination, resulting in low quantum efficiency. Furthermore, SrTiO3 materials also have drawbacks such as small specific surface area and limited exposed catalytic active sites, all of which reduce photocatalytic activity.
[0007] Therefore, how to utilize the polarized electric field generated by BiFeO3 under ultrasound to promote the separation of photogenerated electron-hole pairs, and the advantages of SrTiO3's high activity, high thermoelectric power, dielectric constant, and metallic conductivity, while overcoming the disadvantages of SrTiO3 material such as severe photogenerated electron-hole pair recombination, low quantum efficiency, and low photocatalytic activity, to prepare a piezoelectric photocatalytic composite material with excellent comprehensive performance is currently a key research issue. Summary of the Invention
[0008] To address the shortcomings of existing technologies, the present invention aims to provide a SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material, its preparation method, and its application, thereby solving the problems of severe photogenerated electron-hole pair recombination, low quantum efficiency, and low photocatalytic activity in current SrTiO3 materials.
[0009] To achieve the above objectives, the present invention adopts the following technical solution:
[0010] This invention proposes a SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material, wherein the composite material is based on BiFeO3, and SrTiO3 derived from a monolayer of Ti3C2 is uniformly dispersed on the surface of BiFeO3.
[0011] Preferably, the mass of BiFeO3 in the composite material is 10-50% of the mass of SrTiO3.
[0012] This invention also proposes a method for preparing SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material, comprising the following steps:
[0013] S1. Dissolve KOH in deionized water and mix well to obtain a KOH solution. Then add Bi(NO3)3·5H2O and Fe(NO3)3·9H2O to the KOH solution, stir to obtain a mixed solution, sonicate, and then transfer the mixed solution to a reaction vessel and place it in an oven at 180-200℃ for 8-10 hours. After the reaction is completed, a precipitate is obtained. Cool, then centrifuge, wash and dry the precipitate to obtain reddish-brown BiFeO3 solid.
[0014] S2. Add LiF powder to a beaker containing HCl solution and stir to obtain LiF solution. Weigh Ti3AlC2 powder and add it to the LiF solution. Then heat and stir in an oil bath to etch. After etching is complete, wash with deionized water, adjust the pH value to make the solution neutral, centrifuge the solution to obtain a viscous precipitate, disperse the precipitate in deionized water, protect it with flowing argon gas, and sonicate it in an ultrasonic cleaner to obtain a dark green monolayer Ti3C2 colloid, which is then frozen and stored.
[0015] S3. Sr(OH)2·8H2O powder was dissolved in deionized water to obtain a strontium hydroxide solution. The monolayer Ti3C2 colloid was then dispersed in the strontium hydroxide solution, and the BiFeO3 solid was added. The mixture was then transferred to a reaction vessel and placed in a homogeneous reactor. The reaction temperature was set to 180–200 °C, and the homogeneous rotation speed was set to 5–20 r / min. After the reaction was completed, the mixture was cooled, washed with deionized water, and the pH value was adjusted to make the solution neutral. The solution was centrifuged to obtain a precipitate. The solid sample was then placed in a muffle furnace for calcination to obtain the SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material.
[0016] Preferably, in step S1, the stirring time is 30-60 min; the ultrasonication time is 30-60 min.
[0017] Preferably, in step S1, the drying temperature is 50–70°C, and the drying time is 10–14 hours.
[0018] The mass ratio of KOH, Bi(NO3)3·5H2O and Fe(NO3)3·9H2O is (15-18):(3-6):(2-5).
[0019] Preferably, in step S2, the etching temperature is 50–70°C, and the etching time is 40–48 h.
[0020] Preferably, the HCl solution is prepared by mixing concentrated hydrochloric acid and water in a volume ratio of 3 to 4:1.
[0021] Preferably, in step S3, the mass ratio of the Sr(OH)2·8H2O powder to BiFeO3 is 8 to 16:1.
[0022] Preferably, in step S3, the rotational speed in the homogeneous reactor is 5 to 20 r / min.
[0023] Preferably, in step S3, the calcination temperature is 500–800°C; the drying temperature is 50–70°C; and the drying time is 10–14 hours.
[0024] This invention further proposes the application of the SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material in the complete water splitting to produce hydrogen and oxygen under piezoelectric photocatalysis.
[0025] The application specifically includes the following steps: pre-treating a certain mass percentage of co-catalyst (0.1wt% Rh, 0.05wt% Cr, 0.05wt% Co) by photodepositing the SrTiO3 / BiFeO3 piezoelectric photocatalyst, then ultrasonically dispersing it in deionized water, evacuating the system to remove air, introducing argon gas, and carrying out the catalytic reaction under the combined action of visible light and ultrasound, and using gas chromatography to test the hydrogen and oxygen production under piezoelectric photocatalysis.
[0026] The visible light is provided by a 300W xenon lamp (full spectrum, current intensity of 16A), and the mechanical force is provided by an ultrasonic cleaner (50-120W). To avoid the influence of thermal effects, the temperature of the entire system is controlled at 8°C using circulating cooling water throughout the process.
[0027] The present invention characterizes the above-mentioned SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material using instruments such as X-ray powder diffraction and transmission electron microscopy.
[0028] Compared with the prior art, the present invention has the following beneficial effects:
[0029] The SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material provided by this invention is formed by in-situ derivation of SrTiO3 on the surface of BiFeO3 via a hydrothermal method. The synthesis conditions are simple and easy to operate. SrTiO3 has excellent light absorption in the ultraviolet region. SrTiO3 derived from monolayer Ti3C2 has a large specific surface area, exposing more active sites, which can improve photocatalytic activity. BiFeO3 can form a polarized electric field under ultrasonic action, providing a driving force for photoinduced charge and inhibiting photogenerated electron-hole recombination. This helps the SrTiO3 / BiFeO3 composite material achieve efficient and stable piezoelectric photocatalytic water splitting reaction performance without the need for sacrificial agents or additional ionic electronic media. Attached Figure Description
[0030] Figure 1 The X-ray powder diffraction pattern of the SrTiO3 / BiFeO3 composite material prepared in Example 1 of this invention;
[0031] Figure 2 This is a transmission electron microscope image of the SrTiO3 / BiFeO3 composite material prepared in Example 1 of the present invention;
[0032] Figure 3The UV-Vis diffuse reflectance absorption spectrum of the SrTiO3 / BiFeO3 composite material prepared in Example 1 of this invention;
[0033] Figure 4 The diagram shows the efficiency of water splitting under piezoelectric photocatalysis for the materials prepared in Examples 1-3 and Comparative Examples 1-3 of this invention.
[0034] Figure 5 The graph shows the efficiency of total water splitting of the SrTiO3 / BiFeO3 composite material prepared in Example 1 of this invention under different ultrasonic powers. Detailed Implementation
[0035] The present invention will be further described in detail below through specific preferred embodiments, but the present invention is not limited to the following embodiments.
[0036] It should be noted that, unless otherwise specified, all chemical reagents involved in this invention were purchased through commercial channels.
[0037] Example 1
[0038] A method for preparing a SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material includes the following steps:
[0039] (1) Dissolve 16.83g of KOH in 30mL of deionized water and sonicate to obtain KOH solution. Then add 4.85g of Bi(NO3)3·5H2O and 3.32g of Fe(NO3)3·9H2O to the above KOH solution and stir for 50min to obtain a mixed solution. Sonicate for 30min and then transfer the mixed solution to a reaction vessel with a polytetrafluoroethylene liner. Place it in an oven at 200℃ for 9h. After the reaction is completed, a precipitate is obtained. Cool the precipitate and then centrifuge, wash and dry it to obtain reddish-brown BiFeO3 solid.
[0040] (2) 2.0 g of LiF powder was slowly added to a polytetrafluoroethylene beaker containing 20 mL of HCl solution (concentration of 9 M) and stirred at room temperature for 1 h to obtain LiF solution. 2.0 g of Ti3AlC2 powder was weighed and slowly added to the LiF solution. The mixture was then heated to 60 °C in an oil bath and stirred for 46 h to etch. After etching was completed, the mixture was washed with deionized water and the pH was adjusted to 7 to make the solution neutral. The solution was centrifuged to obtain a viscous precipitate. The precipitate was then dispersed in deionized water and protected with flowing argon gas. The mixture was then sonicated in an ultrasonic cleaner to obtain a dark green monolayer Ti3C2 colloid, which was then frozen and stored.
[0041] (3) Weigh 4g of Sr(OH)2·8H2O powder and slowly add it to a beaker containing 40mL of deionized water. Stir evenly at room temperature, add 0.76g of monolayer Ti3C2 colloid, and then add 0.25g of BiFeO3 powder. After stirring evenly, transfer the solution to a polytetrafluoroethylene reactor and react in a homogeneous reactor at 180℃ for 2h. The rotation speed in the homogeneous reactor is 5r / min. After the hydrothermal reaction is completed, the reaction solution is washed with deionized water by centrifugation until neutral. The washed product is then dried in a vacuum drying oven at 60℃ for 24h. Finally, the dried sample is calcined in a muffle furnace at 600℃ for 1h to obtain the SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material.
[0042] Example 2
[0043] A method for preparing a SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material includes the following steps:
[0044] (1) Dissolve 16.83g of KOH in 30mL of deionized water and sonicate to obtain KOH solution. Then add 4.85g of Bi(NO3)3·5H2O and 3.32g of Fe(NO3)3·9H2O to the above KOH solution and stir for 50min to obtain a mixed solution. Sonicate for 30min and then transfer the mixed solution to a reaction vessel with a polytetrafluoroethylene liner. Place it in an oven at 200℃ for 9h. After the reaction is completed, a precipitate is obtained. Cool the precipitate and then centrifuge, wash and dry it to obtain reddish-brown BiFeO3 solid.
[0045] (2) 2.0 g of LiF powder was slowly added to a polytetrafluoroethylene beaker containing 20 mL of HCl solution (concentration of 9 M) and stirred at room temperature for 1 h to obtain LiF solution. 2.0 g of Ti3AlC2 powder was weighed and slowly added to the LiF solution. The mixture was then heated to 60 °C in an oil bath and stirred for 46 h to etch. After etching was completed, the mixture was washed with deionized water and the pH was adjusted to 7 to make the solution neutral. The solution was centrifuged to obtain a viscous precipitate. The precipitate was then dispersed in deionized water and protected with flowing argon gas. The mixture was then sonicated in an ultrasonic cleaner to obtain a dark green monolayer Ti3C2 colloid, which was then frozen and stored.
[0046] (3) Weigh 4g of Sr(OH)2·8H2O powder and slowly add it to a beaker containing 40mL of deionized water. Stir evenly at room temperature, add 0.76g of monolayer Ti3C2 colloid, and then add 0.5g of BiFeO3 powder. After stirring evenly, transfer the solution to a polytetrafluoroethylene reactor and react in a homogeneous reactor at 180℃ for 2h. The rotation speed in the homogeneous reactor is 5r / min. After the hydrothermal reaction is completed, the reaction solution is washed with deionized water by centrifugation until neutral. The washed product is then dried in a vacuum drying oven at 60℃ for 24h. Finally, the dried sample is calcined in a muffle furnace at 600℃ for 1h to obtain the SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material.
[0047] Example 3
[0048] A method for preparing a SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material includes the following steps:
[0049] (1) Dissolve 16.83g of KOH in 30mL of deionized water and sonicate to obtain KOH solution. Then add 4.85g of Bi(NO3)3·5H2O and 3.32g of Fe(NO3)3·9H2O to the above KOH solution and stir for 50min to obtain a mixed solution. Sonicate for 30min and then transfer the mixed solution to a reaction vessel with a polytetrafluoroethylene liner. Place it in an oven at 200℃ for 9h. After the reaction is completed, a precipitate is obtained. Cool the precipitate and then centrifuge, wash and dry it to obtain reddish-brown BiFeO3 solid.
[0050] (2) 2.0 g of LiF powder was slowly added to a polytetrafluoroethylene beaker containing 20 mL of HCl solution (concentration of 9 M) and stirred at room temperature for 1 h to obtain LiF solution. 2.0 g of Ti3AlC2 powder was weighed and slowly added to the LiF solution. The mixture was then heated to 60 °C in an oil bath and stirred for 46 h to etch. After etching was completed, the mixture was washed with deionized water and the pH was adjusted to 7 to make the solution neutral. The solution was centrifuged to obtain a viscous precipitate. The precipitate was then dispersed in deionized water and protected with flowing argon gas. The mixture was then sonicated in an ultrasonic cleaner to obtain a dark green monolayer Ti3C2 colloid, which was then frozen and stored.
[0051] (3) Weigh 4g of Sr(OH)2·8H2O powder and slowly add it to a beaker containing 40mL of deionized water. Stir evenly at room temperature, add 0.76g of monolayer Ti3C2 colloid, and then add 0.25g of BiFeO3 powder. After stirring evenly, transfer the solution to a polytetrafluoroethylene reactor and react in a homogeneous reactor at 180℃ for 2h. The rotation speed in the homogeneous reactor is 5r / min. After the hydrothermal reaction is completed, the reaction solution is washed with deionized water by centrifugation until neutral. The washed product is then dried in a vacuum drying oven at 60℃ for 24h. Finally, the dried sample is calcined in a muffle furnace at 800℃ for 1h to obtain the SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material.
[0052] Example 4
[0053] A method for preparing a SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material includes the following steps:
[0054] (1) Dissolve 16.83g of KOH in 30mL of deionized water and sonicate to obtain KOH solution. Then add 4.85g of Bi(NO3)3·5H2O and 3.32g of Fe(NO3)3·9H2O to the above KOH solution and stir for 50min to obtain a mixed solution. Sonicate for 30min and then transfer the mixed solution to a reaction vessel with a polytetrafluoroethylene liner. Place it in an oven at 200℃ for 9h. After the reaction is completed, a precipitate is obtained. Cool the precipitate and then centrifuge, wash and dry it to obtain reddish-brown BiFeO3 solid.
[0055] (2) 2.0 g of LiF powder was slowly added to a polytetrafluoroethylene beaker containing 20 mL of HCl solution (concentration of 9 M). The mixture was stirred at room temperature for 1 h to obtain LiF solution. 2.0 g of Ti3AlC2 powder was weighed and slowly added to the LiF solution. The mixture was then heated to 50 °C in an oil bath and stirred for 46 h to etch. After etching was completed, the mixture was washed with deionized water and the pH was adjusted to 7 to make the solution neutral. The solution was centrifuged to obtain a viscous precipitate. The precipitate was then dispersed in deionized water and protected with flowing argon gas. The mixture was then sonicated in an ultrasonic cleaner to obtain a dark green monolayer Ti3C2 colloid, which was then frozen and stored.
[0056] (3) Weigh 4g of Sr(OH)2·8H2O powder and slowly add it to a beaker containing 40mL of deionized water. Stir evenly at room temperature, add 0.76g of monolayer Ti3C2 colloid, and then add 0.5g of BiFeO3 powder. After stirring evenly, transfer the solution to a polytetrafluoroethylene reactor and react in a homogeneous reactor at 180℃ for 2h. The rotation speed in the homogeneous reactor is 10r / min. After the hydrothermal reaction is completed, the reaction solution is washed with deionized water by centrifugation until neutral. The washed product is then dried in a vacuum drying oven at 60℃ for 24h. Finally, the dried sample is calcined in a muffle furnace at 800℃ for 1h to obtain the SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material.
[0057] Example 5
[0058] A method for preparing a SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material includes the following steps:
[0059] (1) Dissolve 16.83g of KOH in 30mL of deionized water and sonicate to obtain KOH solution. Then add 4.85g of Bi(NO3)3·5H2O and 3.32g of Fe(NO3)3·9H2O to the above KOH solution and stir for 50min to obtain a mixed solution. Sonicate for 30min and then transfer the mixed solution to a reaction vessel with a polytetrafluoroethylene liner. Place it in an oven at 200℃ for 9h. After the reaction is completed, a precipitate is obtained. Cool the precipitate and then centrifuge, wash and dry it to obtain reddish-brown BiFeO3 solid.
[0060] (2) 2.0 g of LiF powder was slowly added to a polytetrafluoroethylene beaker containing 20 mL of HCl solution (concentration of 9 M). The mixture was stirred at room temperature for 1 h to obtain LiF solution. 2.0 g of Ti3AlC2 powder was weighed and slowly added to the LiF solution. The mixture was then heated to 70 °C in an oil bath and stirred for 46 h to etch. After etching was completed, the mixture was washed with deionized water and the pH was adjusted to 7 to make the solution neutral. The solution was centrifuged to obtain a viscous precipitate. The precipitate was then dispersed in deionized water and protected with flowing argon gas. The mixture was then sonicated in an ultrasonic cleaner to obtain a dark green monolayer Ti3C2 colloid, which was then frozen and stored.
[0061] (3) Weigh 4g of Sr(OH)2·8H2O powder and slowly add it to a beaker containing 40mL of deionized water. Stir evenly at room temperature, add 0.76g of monolayer Ti3C2 colloid, and then add 0.25g of BiFeO3 powder. After stirring evenly, transfer the solution to a polytetrafluoroethylene reactor and react in a homogeneous reactor at 180℃ for 2h. The rotation speed in the homogeneous reactor is 10r / min. After the hydrothermal reaction is completed, the reaction solution is washed with deionized water by centrifugation until neutral. The washed product is then dried in a vacuum drying oven at 60℃ for 24h. Finally, the dried sample is calcined in a muffle furnace at 600℃ for 1h to obtain the SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material.
[0062] Comparative Example 1
[0063] A method for synthesizing a piezoelectric photocatalyst includes the following steps:
[0064] 16.83 g of KOH was dissolved in 30 mL of deionized water and sonicated to obtain a KOH solution. Then, 4.85 g of Bi(NO3)3·5H2O and 3.32 g of Fe(NO3)3·9H2O were added to the KOH solution and stirred for 50 min to obtain a mixed solution. The mixture was then sonicated for 30 min and transferred to a reaction vessel with a polytetrafluoroethylene liner. The mixture was placed in an oven at 200 °C for 9 h. After the reaction was completed, a precipitate was obtained. The precipitate was cooled, centrifuged, washed, and dried to obtain a reddish-brown solid BiFeO3.
[0065] Comparative Example 2
[0066] A method for synthesizing a piezoelectric photocatalyst includes the following steps:
[0067] (1) 2.0g of LiF powder was slowly added to a polytetrafluoroethylene beaker containing 20mL of HCl solution (concentration of 9M). The mixture was stirred at room temperature for 1h to obtain LiF solution. 2.0g of Ti3AlC2 powder was weighed and slowly added to the LiF solution. The mixture was then heated and stirred in an oil bath for 46h to etch. After etching was completed, the mixture was washed with deionized water and the pH was adjusted to 7 to make the solution neutral. The solution was centrifuged to obtain a viscous precipitate. The precipitate was then dispersed in deionized water and protected with flowing argon gas. The mixture was then sonicated in an ultrasonic cleaner to obtain a dark green monolayer Ti3C2 colloid, which was then frozen and stored.
[0068] (2) Weigh 0.5g of Sr(OH)2·8H2O powder and slowly add it to a beaker containing 40mL of deionized water. Stir evenly at room temperature, add 0.1g of monolayer Ti3C2 colloid, stir evenly, and then transfer the solution to a polytetrafluoroethylene reactor. React in a homogeneous reactor at 180℃ for 2h, with a rotation speed of 5r / min. After the hydrothermal reaction is completed, wash the reaction solution with deionized water by centrifugation until neutral, and then dry the washed product in a vacuum drying oven at 60℃ for 24h. Finally, calcine the dried sample in a muffle furnace at 600℃ for 1h to obtain SrTiO3 solid with monolayer Ti3C2 as Ti source.
[0069] Comparative Example 3
[0070] A method for synthesizing a piezoelectric photocatalyst includes the following steps:
[0071] Weigh 2.5g of commercial SrTiO3 powder into an agate mortar, then add 0.25g of BiFeO3 powder, and wet grind for 30 minutes to mix thoroughly, thus obtaining the SrTiO3 / BiFeO3 composite material.
[0072] Application examples
[0073] The catalysts prepared in Examples 1-3 and Comparative Examples 1-3 of this invention were used for photocatalytic water splitting. Before performance evaluation, all catalysts were pretreated by photodepositing a certain mass percentage of co-catalyst (0.1 wt% Rh, 0.05 wt% Cr, 0.05 wt% Co). For performance evaluation, 50 mg of SrTiO3 solid, BiFeO3 solid, and SrTiO3 / BiFeO3 solid were placed in a photocatalytic reactor containing 50 mL of deionized water and connected to a photocatalytic performance evaluation instrument. Before the photocatalytic reaction, the system was evacuated to remove air, and piezoelectric-photocatalytic water splitting tests were performed under a 300 W xenon lamp (full spectrum). The products were analyzed by online gas chromatography equipped with a TCD detector.
[0074] The piezoelectric photocatalysis test process is basically similar to the photocatalysis test process. The main difference is that in the piezoelectric photocatalysis test process, the reactor is placed in an ultrasonic cleaner (50-120W), and a mechanical stress is applied during the reaction.
[0075] Test Results and Analysis
[0076] The crystal phase structure of the SrTiO3 / BiFeO3 composite material prepared in Example 1 was characterized by X-ray powder diffraction (XRD), and the results were obtained. Figure 1 The morphology of the SrTiO3 / BiFeO3 composite material prepared in Example 1 was observed by transmission electron microscopy, and the results were obtained. Figure 2The absorption range of light by the SrTiO3 / BiFeO3 composite material was observed by ultraviolet diffuse reflectance absorption spectroscopy, and the results were obtained. Figure 3 By comparing the efficiency of the composite materials prepared in Examples 1-3 and Comparative Examples 1-3 in the total water splitting under piezoelectric photocatalysis, the following results were obtained. Figure 4 The efficiency of total water splitting of the SrTiO3 / BiFeO3 composite material prepared in Example 1 under different ultrasonic powers was statistically analyzed. Figure 5 .
[0077] Figure 1 The image shows the XRD pattern of the SrTiO3 / BiFeO3 composite material prepared in Example 1. Comparison with the PDF cards of the XRD patterns of bismuth ferrite and strontium titanate confirms the successful preparation of the SrTiO3 / BiFeO3 composite material. Figure 1 As can be seen, the introduction of bismuth ferrite did not change the crystal structure of strontium titanate, and there were no extra impurity peaks in the XRD spectrum, proving that the SrTiO3 / BiFeO3 composite material has excellent purity and crystallinity.
[0078] Figure 2 This is a SEM image of the SrTiO3 / BiFeO3 composite material prepared in Example 1. Bismuth ferrite nanomaterials are cubical bulk materials, while strontium titanate derived from a single layer of Ti3C2 has an irregular cubic shape. Figure 2 As can be seen, many small particles are attached to the surface of the bismuth ferrite nanomaterial, and strontium titanate is uniformly dispersed on the surface of the bismuth ferrite.
[0079] Figure 3 The image shows the UV-vis-DRS diffuse reflectance spectrum of the SrTiO3 / BiFeO3 composite material prepared in Example 1. It can be seen that the SrTiO3 / BiFeO3 composite material has good light absorption in the ultraviolet region.
[0080] Figure 4 This is a graph showing the efficiency of the composite materials prepared in Examples 1-3 and Comparative Examples 1-3 under piezoelectric photocatalysis for water splitting. Compared to Comparative Examples 1-3, Examples 1-3 exhibit better water splitting performance, indicating that the photocatalytic performance of the SrTiO3 / BiFeO3 composite material is higher than that of single SrTiO3 and BiFeO3 materials, and also higher than that of the catalyst obtained by physically mixing SrTiO3 and BiFeO3. Compared to Example 1, Example 2 shows better water splitting performance, indicating that a higher BiFeO3 content results in a stronger piezoelectric effect, which better promotes carrier migration.
[0081] Figure 5 This is a graph showing the efficiency of total water splitting of the SrTiO3 / BiFeO3 composite material prepared in Example 1 under different ultrasonic powers. From... Figure 5As the ultrasonic power increases, the amount of hydrogen and oxygen released from the composite material also increases. This indicates that as the ultrasonic power increases, the piezoelectric effect also increases, which further promotes carrier separation.
[0082] Finally, it should be noted that the above embodiments do not limit the present invention in any way. Those skilled in the art can make modifications and improvements based on the present invention. Therefore, any modifications or improvements made without departing from the spirit of the present invention are within the scope of protection claimed by the present invention.
Claims
1. A method for preparing a SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material, characterized in that, Includes the following steps: S1. Add Bi(NO3)3·5H2O and Fe(NO3)3·9H2O to KOH solution, stir to obtain a mixed solution, sonicate, and then transfer the mixture to a reaction vessel and place it in an oven at 180~200℃ for 8~10h. After the reaction is completed, a precipitate is obtained, cooled, centrifuged, washed and dried to obtain reddish-brown BiFeO3 solid. S2. Weigh Ti3AlC2 powder, add it to LiF solution, heat and stir to etch. After etching is complete, wash and centrifuge to obtain a precipitate. Disperse the precipitate in water, protect it with flowing argon gas, and sonicate to obtain a dark green monolayer Ti3C2 colloid, which is then frozen and stored. S3. Dissolve Sr(OH)2·8H2O powder in deionized water to obtain a strontium hydroxide solution. Then disperse the monolayer Ti3C2 colloid in the strontium hydroxide solution, add the BiFeO3 solid, and then transfer the mixture to a reaction vessel and place it in a homogeneous reactor. Set the reaction temperature to 180~200℃ and the homogeneous rotation speed to 5~20 r / min. After the reaction is completed, cool, wash, and centrifuge to obtain a precipitate. Then calcine the precipitate to obtain the SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material. In step S3, the mass ratio of Sr(OH)2·8H2O powder to BiFeO3 is 8~16:
1.
2. The preparation method of the SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material according to claim 1, characterized in that, In step S1, the stirring time is 30-60 minutes; the ultrasonication time is 30-60 minutes.
3. The preparation method of the SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material according to claim 1, characterized in that, In step S1, the mass ratio of KOH, Bi(NO3)3·5H2O and Fe(NO3)3·9H2O is (15~18):(3~6):(2~5).
4. The method for preparing the SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material according to claim 1, characterized in that, In step S2, the etching temperature is 50~70℃, and the etching time is 40~48h.
5. The preparation method of the SrTiO3 / BiFeO3 piezoelectric photocatalytic composite material according to claim 1, characterized in that, In step S3, the calcination temperature is 500~800℃.