Preparation method for enhancing photo-generated charge space separation of Bi4Ti3O12 ferroelectric material by doping

Abstract

The invention relates to the field of material preparation, in particular to a preparation method for enhancing photo-generated charge space separation of a Bi4Ti3O12 ferroelectric material through doping, and solves the problem that the current original Bi4Ti3O12 charge separation effect is poor. Specifically, NaCl and KCl are weighed according to a set proportion to serve as molten salts, Bi2O3 and TiO2 are added to serve as reactants, doping of different elements is achieved by changing the types of the molten salts or adding other oxides, and the Bi4Ti3O12 photo-generated charge space separation effect is improved. According to the present invention, the preparation is performed through the molten salt method, the operation is simple, the cost is low, and the obtained product has characteristics of regular morphology, high yield, high purity, high photo-generated charge space separation efficiency, and large-scale application potential.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation, specifically a method for enhancing Bi4Ti3O by doping. 12 A method for preparing ferroelectric materials with spatial separation of photogenerated charges. Background Technology

[0002] Bi4Ti3O 12 Bi₄Ti₃O₃ is a typical Aurivillius-type layered ferroelectric material, possessing excellent chemical stability, environmental compatibility, and strong redox capabilities, demonstrating unique application potential in the field of photocatalysis. However, Bi₄Ti₃O₃... 12 The low efficiency of single-cell photocatalysis is mainly due to the layered structure, which leads to high resistance to the interlayer transport of photogenerated electron-hole pairs, high recombination rate, and insufficient carrier separation efficiency. In addition, its carrier mobility is low and charge transport kinetics are slow, which seriously limits its industrial application.

[0003] Doping modification is a key strategy to overcome the aforementioned bottlenecks, especially in improving charge separation efficiency. By doping with metal ions (W), the additional electric field along the c-axis of Bi3TiNbO9 can be controlled, and the depolarization electric field in each layer along the a-axis is also enhanced due to the strengthened structural deformation. Rare earth element (Lu, Yb, Er, Eu, Sm, Nd) doping improves the space charge separation efficiency of BiOCl and significantly improves carrier dynamics. Some dopants can also serve as additional active sites, enhancing the adsorption and activation capabilities of reactant molecules. Furthermore, the doping modification process is simple, cost-controllable, and can achieve improved charge separation efficiency for Bi4Ti3O9. 12 Breakthroughs in the photocatalytic performance of ferroelectric materials provide an efficient and feasible technical means.

[0004] To date, there is no method for enhancing Bi4Ti3O using doping. 12 Methods for preparing photogenerated charges spatially separated from ferroelectric materials are documented or publicly available in patents. This invention employs a molten salt method, using NaCl and KCl as molten salts, and adding Bi₂O₃ and TiO₂ as reactants. The original Bi₄Ti₃O₂ content is increased by changing the type of molten salt or adding other oxides. 12 The photogenerated charge spatial separation effect is simple, low-cost, and produces products with high photocatalytic performance, showing potential for large-scale application. Summary of the Invention

[0005] The purpose of this invention is to provide a method for enhancing Bi4Ti3O by doping. 12 A method for preparing ferroelectric materials with spatial separation of photogenerated charges.

[0006] The technical solution of this invention is:

[0007] A method for enhancing Bi4Ti3O by doping 12 A method for preparing photogenerated charges in ferroelectric materials, solving the current limitations of primitive Bi4Ti3O4 materials. 12 The problem of poor charge separation effect is addressed by weighing NaCl and KCl as molten salts according to a set ratio, adding Bi₂O₃ and TiO₂ as reactants, and synthesizing the original Bi₄Ti₃O₃ through a molten salt method. 12 Changing the type of molten salt or adding other oxides can improve the original Bi4Ti3O 12 Photogenerated charge spatial separation effect.

[0008] The aforementioned Bi4Ti3O4 material enhances the spatial separation efficiency of photogenerated charges. 12 The method for preparing the material is characterized by improving the original Bi₄Ti₃O₃ by changing the type of molten salt or adding other oxides. 12 Photogenerated charge spatial separation effect.

[0009] The aforementioned Bi4Ti3O4 material enhances the spatial separation efficiency of photogenerated charges. 12 The method for preparing the material is characterized in that, during the synthesis process, the type of molten salt is changed, such as one or two of RbCl, CsCl, etc., and the amount of substance is 0.01~0.04 mol (optimal is 0.03 mol).

[0010] The aforementioned Bi4Ti3O4 material enhances the spatial separation efficiency of photogenerated charges. 12 The method for preparing the material is characterized in that, during the synthesis process, other oxides are added, such as Sb2O5 in an amount of 0.025~0.1 mmol (optimally 0.05 mmol) and SnO2 in an amount of 0.05~0.3 mmol (optimally 0.1 mmol).

[0011] The aforementioned Bi4Ti3O4 material enhances the spatial separation efficiency of photogenerated charges. 12 The method for preparing the material is characterized by using NaCl and KCl in a 1:1 ratio as molten salt.

[0012] The aforementioned Bi4Ti3O4 material enhances the spatial separation efficiency of photogenerated charges. 12 The method for preparing the material is characterized in that Bi2O3 and TiO2 are used as reactants in a ratio of 1:1 to 2:3.

[0013] The aforementioned Bi4Ti3O4 material enhances the spatial separation efficiency of photogenerated charges. 12 The method for preparing the material is characterized in that NaCl, KCl, Bi2O3 and TiO2 are ground into powder in a ratio of 10:10:2:3 and then loaded into an Al2O3 crucible.

[0014] The aforementioned Bi4Ti3O4 material enhances the spatial separation efficiency of photogenerated charges. 12 The method for preparing the material is characterized by heating the temperature to 700~900 ℃ (optimal is 800 ℃) at a rate of 5 ℃ / min during the reaction, reacting in a muffle furnace for 1~3 h (optimal is 2 h), and then naturally cooling to room temperature.

[0015] The design concept of this invention is as follows:

[0016] Based on the specific requirements of photocatalysts for charge space separation efficiency, Bi4Ti3O with high efficiency in charge space separation was prepared using inexpensive raw materials as fluxes and reactants. 12 Materials are the design concept of this invention.

[0017] The advantages and beneficial effects of this invention are as follows:

[0018] 1. The photocatalyst of the present invention, which achieves efficient charge space separation, has very high photocatalytic performance and long-term stability, and has the potential for practical application in photocatalytic water splitting.

[0019] 2. This invention utilizes NaCl and KCl as molten salts to lower the reaction temperature. Based on Bi2O3 and TiO2 as reactants, by changing the type of molten salt or adding other oxides, the charge separation efficiency can be significantly improved. This method is low-cost and simple and quick to operate, and has broad application prospects in the field of materials synthesis. Attached Figure Description

[0020] Figure 1 Using NaCl and KCl as molten salts and Bi₂O₃ and TiO₂ as reactants, modified Bi₄Ti₃O₂ can be synthesized in one step via the molten salt method by changing the type of molten salt or adding other oxides. 12 Its appearance.

[0021] Figure 2 Using NaCl and KCl as molten salts and Bi₂O₃ and TiO₂ as reactants, modified Bi₄Ti₃O₂ can be synthesized in one step via the molten salt method by changing the type of molten salt or adding other oxides. 12 The morphology of Bi4Ti3O modified with Sb2O5 doping 12 For example, through Au and MnO x The space charge separation effect can be observed at the location of the photodeposition.

[0022] Figure 3Using NaCl and KCl as molten salts and Bi₂O₃ and TiO₂ as reactants, Sb-modified Bi₄Ti₃O₂ can be synthesized in one step via the molten salt method by changing the type of molten salt or adding other oxides. 12 XRD of Bi4Ti3O2 modified with Sb2O5 doping 12 For example, we study the effect of different doping amounts on the phase. The horizontal axis represents the diffraction angle 2θ (º), and the vertical axis represents the intensity (au).

[0023] Figure 4 Using NaCl and KCl as molten salts and Bi₂O₃ and TiO₂ as reactants, RbCl was added to change the type of molten salt, and Rb-modified Bi₄Ti₃O₂ was synthesized in one step via the molten salt method to obtain Rb-modified Bi₄Ti₃O₂. 12 The performance is shown. The horizontal axis, Time, represents the test time (h), and the vertical axis, Gases evolution, represents the amount of hydrogen and oxygen produced (μmol·h⁻¹). -1 ).

[0024] Figure 5 Using NaCl and KCl as molten salts and Bi₂O₃ and TiO₂ as reactants, a trace amount of Sb₂O₅ was added to synthesize Sb-modified Bi₄Ti₃O₃ in one step via a molten salt method. 12 The performance is shown. The horizontal axis, Time, represents the test time (h), and the vertical axis, Gases evolution, represents the amount of hydrogen and oxygen produced (μmol·h⁻¹). -1 ).

[0025] Figure 6 Using NaCl and KCl as molten salts and Bi₂O₃ and TiO₂ as reactants, a trace amount of SnO₂ was added to synthesize Sn-modified Bi₄Ti₃O₃ in one step via a molten salt method. 12 The performance is shown. The horizontal axis, Time, represents the test time (h), and the vertical axis, Gases evolution, represents the amount of hydrogen and oxygen produced (μmol·h⁻¹). -1 ). Detailed Implementation

[0026] Weigh 0.01 mol of NaCl, KCl, and 0.03 mol of molten salt, and grind them in a mortar until homogeneous and without noticeable granules. Then weigh 2 mmol of Bi₂O₃ and 3 mmol of TiO₂, and grind them together with the molten salt until the color is uniform. Then, place the mixture in an Al₂O₃ crucible and maintain it in a muffle furnace at 800 °C for 2 h, with a heating rate of 5 °C / min. After the reaction is complete and cooled to room temperature, grind the agglomerated product into powder, wash it several times with deionized water to remove impurities, and then dry it overnight in a 60 °C oven.

[0027] Weigh 0.01 mol of NaCl and KCl as molten salts, and grind them in a mortar until homogeneous and without obvious granules. Then weigh 2 mmol of Bi₂O₃, 3 mmol of TiO₂, and 0.05 mmol of Sb₂O₅ (or 0.1 mmol of SnO₂), and grind them together with the molten salts until the color is uniform. Then, place the mixture in an Al₂O₃ crucible and maintain it in a muffle furnace at 800 °C for 2 h, with a heating rate of 5 °C / min. After the reaction is complete and cooled to room temperature, grind the agglomerated product into powder, wash it several times with deionized water to remove impurities, and then dry it overnight in a 60 °C oven.

[0028] The present invention will now be further described in detail with reference to embodiments and accompanying drawings.

[0029] Example 1

[0030] Based on NaCl and KCl as molten salts and Bi₂O₃ and TiO₂ as reactants, modified Bi₄Ti₃O₂ can be synthesized in one step via the molten salt method by changing the type of molten salt or adding other oxides. 12 The object is studied to determine its morphology.

[0031] Morphological characterization equipment: Regulus 8100 scanning electron microscope. Figure 1 Modified Bi4Ti3O 12 Microscopic morphology diagram. (From...) Figure 1 a. It can be seen that the Sb-modified Bi4Ti3O 12 They exhibit a regular nanosheet morphology and uniform size, with a particle size of approximately 1 μm * 0.5 μm. Figure 1 b shows that the Sn-modified Bi4Ti3O 12 It is also a regular nanosheet, with a size compared to Sb-modified Bi4Ti3O 12 Slightly larger, with a particle size of approximately 1 μm * 2 μm. Figure 1 c shows that the Rb-modified Bi4Ti3O 12Similarly, these are regular nanosheets, uniform in size, with a particle size of approximately 1 μm * 2 μm, and a thickness greater than that of Sn-modified Bi4Ti3O. 12 Slightly smaller.

[0032] Example 2

[0033] Based on NaCl and KCl as molten salts and Bi₂O₃ and TiO₂ as reactants, modified Bi₄Ti₃O₂ can be synthesized in one step via the molten salt method by changing the type of molten salt or adding other oxides. 12 As the target, Bi4Ti3O3 modified with Sb2O5 was used. 12 For example, observe the effect of charge space separation.

[0034] Morphological characterization equipment: Regulus 8100 scanning electron microscope. Figure 2 To achieve photodeposition on Sb-modified Bi4Ti3O 12 Surface deposition of Au and MnO x Microscopic images, through Au and MnO x Space charge separation can be observed at the deposition location. As shown in the figure, Au and MnO x The Bi4Ti3O4O4 was deposited on different surfaces of the material, indicating that it was modified by Sb. 12 It has a space charge separation effect.

[0035] Example 3

[0036] Based on NaCl and KCl as molten salts and Bi₂O₃ and TiO₂ as reactants, modified Bi₄Ti₃O₂ can be synthesized in one step via the molten salt method by changing the type of molten salt or adding other oxides. 12 As the target, Bi4Ti3O3 modified with Sb2O5 was used. 12 For example, we studied the effect of different doping amounts on the phase.

[0037] X-ray testing equipment and conditions: D-MAX 2500 / PC, Cu Ka rays. Figure 3 Bi4Ti3O modified with different Sb element contents 12 XRD patterns of the nanosheets. The figures show the effects of different Sb content on Bi₄Ti₃O₄ modification. 12 Peak shape and original Bi4Ti3O 12 The match is perfect, and no other impurities are generated.

[0038] Example 4

[0039] Based on NaCl and KCl as molten salts and Bi₂O₃ and TiO₂ as reactants, modified Bi₄Ti₃O₂ can be synthesized in one step via the molten salt method by changing the type of molten salt or adding other oxides. 12 The photocatalytic water splitting performance of this material was studied.

[0040] The photocatalytic water splitting test was conducted in a 250 ml quartz reactor equipped with a highly sealed fully automated online analysis system (Beijing Perfectlight Technology Co., Ltd., Labsolar-6A). A 300 W xenon lamp (Beijing Perfectlight Technology Co., Ltd., PLS-SXE300D) was used as the light source. To mitigate the impact of increased system temperature due to the heat generated by the light on material properties, the circulating water temperature was maintained at approximately 10 °C. High-purity argon was used as the carrier gas to transport the oxygen and hydrogen produced in the reaction to a gas chromatograph for detection. In the water splitting test, 50 mg of Bi₄Ti₃O₃ was weighed... 12 The sample was dissolved in 100 ml of deionized water and sonicated for 5 min to ensure uniform dispersion. Then, 0.1 wt% Rh, Cr₂O₃, and CoO₂ were sequentially photoprecipitated for 30 min. x As a co-catalyst, air in the reactor and system was then evacuated using a vacuum pump until the software baseline level was reached, and testing began.

[0041] The results of the embodiments show that the present invention provides a method for enhancing Bi4Ti3O by doping. 12 The preparation method of photogenerated charge spatial separation in ferroelectric materials can improve the original Bi4Ti3O by changing the type of molten salt or adding other oxides. 12 Photogenerated charge spatial separation effect, prepared modified Bi4Ti3O 12 It exhibits high catalytic activity and stability. This method is simple to operate, low in cost, and yields products with regular morphology, high yield and purity. Furthermore, it demonstrates high spatial separation efficiency of photogenerated charges, making it a promising candidate for large-scale application.

Claims

1. A method for enhancing Bi4Ti3O by doping 12 A method for preparing photogenerated charges in ferroelectric materials, solving the current limitations of primitive Bi4Ti3O4 materials. 12 The problem of poor charge separation and low photocatalytic activity was addressed. Specifically, NaCl and KCl were weighed out in a predetermined ratio as molten salts, with Bi₂O₃ and TiO₂ as reactants. The effect of Bi₄Ti₃O₂ could be improved by changing the type of molten salt or adding other oxides. 12 Photogenerated charge spatial separation effect.

2. A Bi₄Ti₃O₄ compound with enhanced photogenerated charge spatial separation efficiency according to claim 1. 12 The method for preparing the material is characterized by, The original Bi₄Ti₃O₃ can be improved by changing the type of molten salt or adding other oxides. 12 Photogenerated charge spatial separation effect.

3. A Bi4Ti3O4 composition for enhancing the spatial separation efficiency of photogenerated charges according to claim 2. 12 The method for preparing the material is characterized by, During the synthesis process, the type of molten salt is changed, such as one or two of RbCl and CsCl, with a substance amount of 0.01~0.04 mol (optimal is 0.03 mol).

4. A Bi4Ti3O4 compound with enhanced photogenerated charge spatial separation efficiency according to claim 2. 12 The method for preparing the material is characterized by, During the synthesis process, other oxides are added, such as 0.025~0.1 mmol of Sb2O5 (0.05 mmol optimal) and 0.05~0.3 mmol of SnO2 (0.1 mmol optimal).

5. A Bi₄Ti₃O₄ compound with enhanced photogenerated charge spatial separation efficiency according to claim 1. 12 The method for preparing the material is characterized by, NaCl and KCl were used as molten salt in a 1:1 ratio.

6. A Bi₄Ti₃O₄ compound with enhanced photogenerated charge spatial separation efficiency according to claim 1. 12 The method for preparing the material is characterized by, The ratio of Bi2O3 to TiO2 is 1:1 to 1:1.5 as reactants.

7. A Bi₄Ti₃O₄ compound with enhanced photogenerated charge spatial separation efficiency according to claim 1. 12 The method for preparing the material is characterized by, NaCl, KCl, Bi2O3 and TiO2 are ground into powder in a ratio of 10:10:2:3 and then placed into an Al2O3 crucible.

8. A Bi₄Ti₃O₄ compound with enhanced photogenerated charge spatial separation efficiency according to claim 1. 12 The method for preparing the material is characterized by, The temperature was increased to 700-900 °C (optimal 800 °C) at a rate of 5 °C / min during the reaction, and the reaction was carried out in a muffle furnace for 1-3 h (optimal 2 h), and then naturally cooled to room temperature.

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