A method for preparing TiO2-Bi2O(OH)2SO4 nanocomposites by a synergistic reaction

Abstract

The present invention relates to the field of photocatalysis technology and provides a method for preparing a TiO2-Bi2O(OH)2SO4 nanocomposite through a synergistic reaction. Sodium bismuthate dihydrate, sodium sulfite, and titanium sulfate are added to a hydrothermal reaction kettle containing distilled water to obtain a solid-liquid mixture. Under hydrothermal conditions, the TiO2-Bi2O(OH)2SO4 nanocomposite is prepared through the synergistic effect of the hydrolysis and crystallization reaction of titanium sulfate and the heterogeneous interface in-situ redox reaction of sodium bismuthate dihydrate. The advantages of the present invention are as follows: Based on the synthesis strategy of the synergistic effect of the hydrolysis and crystallization reaction and the heterogeneous interface in-situ redox reaction, the TiO2-Bi2O(OH)2SO4 nanocomposite is prepared, and the preparation steps are simple and the operation is convenient, and the composite effect between TiO2 and Bi2O(OH)2SO4 is good.

Description

Technical Field

[0001] The present invention relates to the field of photocatalysis technology, and particularly to a method for preparing TiO2-Bi2O(OH)2SO4 nanocomposites by a synergistic reaction. Background Art

[0002] Since the discovery in 1972 that titanium dioxide semiconductors have the performance of photocatalytic water splitting for hydrogen production, semiconductor photocatalysis technology has received extensive attention and emphasis from the academic and industrial communities.

[0003] However, when using a single pure titanium dioxide photocatalytic material, photo-generated electrons and holes are prone to recombination, resulting in a decrease in the photoquantum efficiency. Therefore, preventing the recombination of photo-generated electrons and holes and improving the photocatalytic efficiency have become one of the major challenges in the field of photocatalysis research. At the same time, in the practical application of photocatalysis technology, the activity and stability of photocatalytic materials are crucial.

[0004] As is well known in the art, the preparation of composite semiconductor photocatalytic materials is one of the effective methods to prevent the recombination of photo-generated electrons and holes and improve the photocatalytic efficiency. At the same time, existing research shows that Bi2O(OH)2SO4 is a potential excellent photocatalytic material. Therefore, the combination of two semiconductors, namely nano-titanium dioxide TiO2 and bismuth hydroxy sulfate Bi2O(OH)2SO4, is expected to improve the stability and photocatalytic efficiency of the material.

[0005] However, the current preparation methods of nano-TiO2 mainly include chemical reduction method, chemical precipitation method and vapor deposition method, and Bi2O(OH)2SO4 mostly adopts homogeneous hydrothermal method. Although the above methods can prepare single nano-TiO2 and Bi2O(OH)2SO4, when preparing TiO2-Bi2O(OH)2SO4 composites, usually one or two single semiconductors are first prepared, and then physical or chemical composite treatment is carried out. The steps are cumbersome, and it is difficult for the two semiconductors to form an atomic or molecular level heterostructure, resulting in poor composite effect.

[0006] Therefore, it is necessary to develop a method for preparing TiO2-Bi2O(OH)2SO4 nanocomposites with simple steps, convenient operation and good composite effect. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for preparing TiO2-Bi2O(OH)2SO4 nanocomposites by a synergistic reaction. Based on the synthesis strategy of the synergistic effect of hydrolysis crystallization reaction and heterogeneous interface in-situ redox reaction, TiO2-Bi2O(OH)2SO4 nanocomposites are prepared, and the preparation steps are simple, the operation is convenient, and the composite effect between TiO2 and Bi2O(OH)2SO4 is good.

[0008] The present invention adopts the following technical solutions to solve the above technical problems:

[0009] A method for preparing TiO2-Bi2O(OH)2SO4 nanocomposites by a synergistic reaction. Sodium bismuthate dihydrate, sodium sulfite and titanium sulfate are added into a hydrothermal reactor containing distilled water to obtain a solid-liquid mixture. Under hydrothermal conditions, the TiO2-Bi2O(OH)2SO4 nanocomposites are prepared through the synergistic effect of the hydrolysis and crystallization reaction of titanium sulfate and the heterogeneous interface in-situ redox reaction of sodium bismuthate dihydrate. The reaction process is as follows:

[0010] 。

[0011] As one of the preferred embodiments of the present invention, the molar ratio of sodium bismuthate dihydrate, sodium sulfite and titanium sulfate is 2:2:1.

[0012] As one of the preferred embodiments of the present invention, the solid-liquid mixture reacts for 6 - 30 h under hydrothermal conditions at 190 °C.

[0013] As one of the preferred embodiments of the present invention, after the hydrothermal reaction, it further includes the steps of centrifugal separation of the reaction product, washing with distilled water, and vacuum drying to finally obtain the TiO2-Bi2O(OH)2SO4 nanocomposites.

[0014] As one of the preferred embodiments of the present invention, the specific conditions for vacuum drying are: vacuum drying at 60 °C and a vacuum degree of 0.1 Mpa for 2 h.

[0015] As one of the preferred embodiments of the present invention, in the finally obtained TiO2-Bi2O(OH)2SO4 nanocomposite product, the average grain size of TiO2 is 11.0 - 18.1 nm, and the average grain size of Bi2O(OH)2SO4 is 87.2 - 87.4 nm.

[0016] Reaction principle:

[0017] Sodium bismuthate dihydrate is a poorly soluble solid substance, which is transformed into Bi2O(OH)2SO4 through a heterogeneous interface in-situ redox reaction. Among them, sodium bismuthate dihydrate acts as a sacrificial template, and Bi2O(OH)2SO4 is generated on the surface of the template. At the same time, the hydrated titanium dioxide solid produced by the hydrolysis of Ti(SO4)2 in the aqueous solution is also deposited on the surface of the sodium bismuthate dihydrate solid template and further crystallizes into titanium dioxide crystals, thereby generating the TiO2-Bi2O(OH)2SO4 nanocomposite. In the above reaction system, the hydrolysis reaction of Ti(SO4)2 produces hydrogen ions to provide an acidic environment, which ensures that the reduction product of sodium bismuthate dihydrate is bismuthyl hydroxy sulfate Bi2O(OH)2SO4. At the same time, the interfacial redox reaction of sodium bismuthate dihydrate can produce hydroxide ions, promoting the hydrolysis reaction of Ti(SO4)2. The hydrolysis reaction of Ti(SO4)2 and the interfacial redox reaction of sodium bismuthate dihydrate act synergistically to promote the two reactions to proceed completely, and finally the TiO2-Bi2O(OH)2SO4 nanocomposite is obtained.

[0018] The advantages of the present invention compared with the prior art are as follows:

[0019] (1) Based on the synthesis strategy of the synergistic effect of hydrolysis crystallization reaction and heterogeneous interface in-situ redox reaction, the present invention realizes the "one-step" preparation of the TiO2-Bi2O(OH)2SO4 nanocomposite, with simple preparation steps and convenient operation;

[0020] (2) During the preparation of the composite of the present invention, when the hydrated titanium dioxide solid is generated, it is deposited on the sodium bismuthate dihydrate solid template. At the same time, the sodium bismuthate dihydrate solid is in-situ transformed into Bi2O(OH)2SO4. Therefore, Bi2O(OH)2SO4 and TiO2 can effectively form an atomic or molecular heterostructure, with good composite effect;

[0021] (3) During the preparation of the composite of the present invention, the hydrolysis reaction of Ti(SO4)2 produces hydrogen ions to provide an acidic environment, which ensures that the reduction product of sodium bismuthate dihydrate is bismuthyl hydroxy sulfate Bi2O(OH)2SO4; at the same time, the interfacial redox reaction of sodium bismuthate dihydrate can produce hydroxide ions, promoting the hydrolysis reaction of Ti(SO4)2;

[0022] (4) The preparation process of the composite of the present invention is easy to control and reduces the agglomeration of product particles (in-situ transformation and deposition on the solid surface can inhibit the migration of product particles and reduce aggregation and agglomeration), which is easy for industrial production. Description of the Drawings

[0023] Figure 1 It is the TEM image of the product prepared in Example 2 of the present invention (in the figure, the scale bar length is 500 nm);

[0024] Figure 2 XRD patterns of the products prepared in the examples and comparative examples of the present invention (referring to the XRD of titanium dioxide and bismuthyl hydroxy sulfate). Detailed implementation manners

[0025] The following is a detailed description of the embodiments of the present invention. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments. At the same time, the reagent products and experimental methods used in the following examples, comparative examples and experimental examples, unless otherwise specified, are all conventional reagents or methods in the art and will not be elaborated.

[0026] Example 1

[0027] A method for co-reaction to prepare TiO2-Bi2O(OH)2SO4 nanocomposites in this example:

[0028] (1) Add 0.01 mol of sodium bismuthate dihydrate, 0.01 mol of sodium sulfite and 0.005 mol of titanium sulfate to a 50 ml hydrothermal reaction kettle containing 40 ml of distilled water to obtain a solid-liquid mixture.

[0029] (2) React the solid-liquid mixture obtained in step (1) under hydrothermal conditions at 190 °C for 6 h. Through the synergistic effect of the hydrolysis crystallization reaction of titanium sulfate and the heterogeneous interface in-situ redox reaction of sodium bismuthate dihydrate, TiO2-Bi2O(OH)2SO4 is prepared. The reaction process is as follows:

[0030] .

[0031] (3) Centrifuge, wash with distilled water, and vacuum dry the product obtained in step (2) at 60 °C and a vacuum degree of 0.1 Mpa for 2 h to obtain the target product TiO2-Bi2O(OH)2SO4 nanocomposites.

[0032] Example 2

[0033] A method for co-reaction to prepare TiO2-Bi2O(OH)2SO4 nanocomposites in this example:

[0034] (1) Add 0.01 mol of sodium bismuthate dihydrate, 0.01 mol of sodium sulfite and 0.005 mol of titanium sulfate to a 50 ml hydrothermal reaction kettle containing 40 ml of distilled water to obtain a solid-liquid mixture.

[0035] (2) React the solid-liquid mixture obtained in step (1) under hydrothermal conditions at 190 °C for 10 h. Through the synergistic effect of the hydrolysis crystallization reaction of titanium sulfate and the in-situ redox reaction at the heterogeneous interface of sodium bismuthate dihydrate, TiO₂-Bi₂O(OH)₂SO₄ is prepared. The reaction process is as follows:

[0036] .

[0037] (3) Centrifuge and separate the product obtained in step (2), wash it with distilled water, and vacuum dry it at 60 °C and a vacuum degree of 0.1 Mpa for 2 h to obtain the target product TiO₂-Bi₂O(OH)₂SO₄ nanocomposite.

[0038] Example 3

[0039] A method for preparing TiO₂-Bi₂O(OH)₂SO₄ nanocomposite by synergistic reaction in this example:

[0040] (1) Add 0.01 mol of sodium bismuthate dihydrate, 0.01 mol of sodium sulfite, and 0.005 mol of titanium sulfate to a 50 ml hydrothermal reaction kettle containing 40 ml of distilled water to obtain a solid-liquid mixture.

[0041] (2) React the solid-liquid mixture obtained in step (1) under hydrothermal conditions at 190 °C for 20 h. Through the synergistic effect of the hydrolysis crystallization reaction of titanium sulfate and the in-situ redox reaction at the heterogeneous interface of sodium bismuthate dihydrate, TiO₂-Bi₂O(OH)₂SO₄ is prepared. The reaction process is as follows:

[0042] .

[0043] (3) Centrifuge and separate the product obtained in step (2), wash it with distilled water, and vacuum dry it at 60 °C and a vacuum degree of 0.1 Mpa for 2 h to obtain the target product TiO₂-Bi₂O(OH)₂SO₄ nanocomposite.

[0044] Example 4

[0045] A method for preparing TiO₂-Bi₂O(OH)₂SO₄ nanocomposite by synergistic reaction in this example:

[0046] (1) Add 0.01 mol of sodium bismuthate dihydrate, 0.01 mol of sodium sulfite, and 0.005 mol of titanium sulfate to a 50 ml hydrothermal reaction kettle containing 40 ml of distilled water to obtain a solid-liquid mixture.

[0047] (2) React the solid-liquid mixture obtained in step (1) under hydrothermal conditions at 190 °C for 30 h. Through the synergistic effect of the hydrolysis and crystallization reaction of titanium sulfate and the heterogeneous interface in-situ redox reaction of sodium bismuthate dihydrate, TiO2-Bi2O(OH)2SO4 is prepared. The reaction process is as follows:

[0048] .

[0049] (3) Centrifuge and separate the product obtained in step (2), wash it with distilled water, and vacuum dry it at 60 °C and a vacuum degree of 0.1 Mpa for 2 h to obtain the target product TiO2-Bi2O(OH)2SO4 nanocomposite.

[0050] Comparative Example

[0051] A method for preparing a composite in this comparative example is basically the same as that in Example 2, and the main difference is that: titanium sulfate is not added.

[0052] Experimental Example 1

[0053] Place the product prepared in the above example (taking Example 2 as an example) under a transmission electron microscope (TEM) for observation, and the results are as Figure 1 shown.

[0054] From Figure 1 it can be seen that TiO2 (small particles) is loaded on the surface of Bi2O(OH)2SO4 (large particles), indicating the successful synthesis of TiO2-Bi2O(OH)2SO4 of the present invention.

[0055] Experimental Example 2

[0056] Perform X-ray diffraction analysis (XRD analysis) on the products obtained in the above examples and comparative examples, and the results are as Figure 2 shown.

[0057] Figure 2 is the XRD pattern of the products prepared in each example and comparative example of the present invention, with titanium dioxide (PDF#84-1286) and bismuthyl hydroxy sulfate (PDF#76-1102) as references. From Figure 2 it can be seen that: in the XRD patterns of the products of each example, there are obvious characteristic diffraction peaks of TiO2 and Bi2O(OH)2SO4, and there are no diffraction peaks of other substances, indicating that the products of each example are only composed of TiO2 and Bi2O(OH)2SO4 crystals; while in the XRD pattern of the product obtained in the comparative example, there is no characteristic diffraction peak of Bi2O(OH)2SO4, indicating that the product of the comparative example is not Bi2O(OH)2SO4 crystal but other substances; the above XRD analysis shows that in the absence of "titanium sulfate", an acidic environment cannot be provided, and the reaction of sodium bismuthate dihydrate and sodium sulfite cannot obtain Bi2O(OH)2SO4 product.

[0058] In addition, according to the XRD analysis of the products of Examples 1, 2, 3, and 4, and calculated using the Scherrer formula, in the products of Examples 1, 2, 3, and 4: the average grain sizes of TiO2 are 11.0 nm, 13.3 nm, 16.4 nm, and 18.1 nm respectively, and the average grain sizes of Bi2O(OH)2SO4 are 87.2 nm, 87.3 nm, 87.4 nm, and 87.4 nm respectively; it shows that with the extension of the reaction time, the average grain size of TiO2 in the product increases slowly, but the average grain size of Bi2O(OH)2SO4 hardly changes.

[0059] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing TiO2-Bi2O(OH)2SO4 nanocomposites by a synergistic reaction, characterized in that, Sodium bismuthate dihydrate, sodium sulfite and titanium sulfate were added to a hydrothermal reactor containing distilled water to obtain a solid-liquid mixture; under hydrothermal conditions, the TiO2-Bi2O(OH)2SO4 nanocomposite was prepared through the synergistic effect of the hydrolysis crystallization reaction of titanium sulfate and the heterogeneous interface in-situ redox reaction of sodium bismuthate dihydrate. The reaction process is as follows: 。 2. The method for preparing the TiO2-Bi2O(OH)2SO4 nanocomposite by the synergistic reaction according to claim 1, characterized in that, The molar ratio of sodium bismuthate dihydrate, sodium sulfite and titanium sulfate is 2:2:

1.

3. The method for preparing the TiO2-Bi2O(OH)2SO4 nanocomposite by the synergistic reaction according to claim 1, characterized in that, The solid-liquid mixture reacts for 6 - 30 h under hydrothermal conditions at 190 °C.

4. The method for preparing the TiO2-Bi2O(OH)2SO4 nanocomposite by the synergistic reaction according to any one of claims 1 to 3, characterized in that, After the hydrothermal reaction, it also includes the steps of centrifugal separation of the reaction product, washing with distilled water, and vacuum drying to finally obtain the TiO2-Bi2O(OH)2SO4 nanocomposite.

5. The method for preparing the TiO2-Bi2O(OH)2SO4 nanocomposite by the synergistic reaction according to claim 4, characterized in that, The specific conditions for the vacuum drying are: vacuum drying for 2 h at 60 °C and a vacuum degree of 0.1 Mpa.

6. The method for preparing TiO2-Bi2O(OH)2SO4 nanocomposite by synergetic reaction according to claim 4, wherein, In the finally obtained TiO2-Bi2O(OH)2SO4 nanocomposite product, the average grain size of TiO2 is 11.0 - 18.1 nm, and the average grain size of Bi2O(OH)2SO4 is 87.2 - 87.4 nm.

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