Bismuth titanium oxyhalide material and its preparation method and application

Abstract

A bismuth titanium oxyhalide material and its preparation method and application. The material is a new type of bismuth titanium oxyhalide material with a layered structure and has the following structural formula: Bi5Ti2O 11 X, wherein X is Cl, Br, I. The preparation method comprises: mixing Bi2O3, TiO2 and BiOX according to a standard stoichiometric ratio, adding molten salt and grinding, calcining at 750-900°C for 10-30 hours; washing and drying the calcined sample to obtain Bi5Ti2O 11 X material. The preparation method is simple in process, easy to operate and has no secondary pollution.

Description

Technical Field

[0001] The present invention relates to the fields of semiconductor materials and photocatalysis technology, and in particular to a bismuth titanium oxyhalide material and a preparation method and application thereof. Technical Background

[0002] Currently common metal oxide semiconductors such as TiO2 (~3.2eV) have a large band gap and are difficult to utilize in the visible light region, which accounts for about 40% of the solar spectrum. BiOX (X = F, Cl, Br or I) has a smaller band gap and good visible light absorption compared to traditional metal oxide semiconductors. Specifically, the Sillén phase BiOX has a band gap of less than 3.0eV, which enables its application in photocatalytic technology. However, BiOX has low photostability due to the p-orbital contribution of the main halogen in its valence band. There is still a need to research and develop new bismuth titanium oxyhalide materials. Summary of the invention

[0003] In view of this, the main purpose of the present invention is to provide a new bismuth titanium oxyhalide material and a preparation method and application thereof, in order to at least partially solve at least one of the above-mentioned technical problems.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] As one aspect of the present invention, a bismuth titanium oxyhalide material is provided, having the following structural formula: Bi5Ti2O 11 X, wherein X is Cl, Br or I.

[0006] As another aspect of the present invention, a method for preparing the bismuth titanium oxyhalide material as described above is provided, comprising mixing Bi2O3, TiO2 and BiOX according to a standard stoichiometric ratio, adding molten salt to the obtained mixture, grinding it thoroughly, calcining it at 750-900°C for 10-30 hours, repeatedly washing the calcined sample to remove the molten salt, and drying the washed sample to obtain Bi5Ti2O 11 X.

[0007] As another aspect of the present invention, there is provided a use of the bismuth titanium oxyhalide material as described above in a photocatalytic material.

[0008] Compared with the prior art, the novel bismuth titanium oxyhalide material of the present invention and its preparation method and application have the following advantages:

[0009] (1) As a novel semiconductor compound, the bismuth titanium oxyhalide of the present invention has a valence band top mainly contributed by the O2p orbital, which inhibits the oxidation of halogens due to photogenerated holes and has high photostability. At the same time, the bismuth titanium oxyhalide with a Sillén-Aurivillius phase structure has the characteristics of a large visible light response range, a small bandgap, and a low recombination rate of photogenerated electrons and holes;

[0010] (2) The present invention utilizes a molten salt method to synthesize bismuth titanium oxyhalide. Specifically, Bi2O3, TiO2 and BiOX are used as raw materials, and bismuth titanium oxyhalide is successfully synthesized by a molten salt calcination method. The preparation method is easy to operate, the process is simple, the raw materials are cheap and readily available, and it is environmentally friendly, and is suitable for industrial mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The crystal structure diagram of bismuth titanium oxyhalide prepared in Example 1 of the present invention;

[0012] Figure 2 The Bi5Ti2O prepared in Example 1 of the present invention 11 XRD pattern of Cl;

[0013] Figure 3 The Bi5Ti2O prepared in Example 1 of the present invention 11 SEM image of C1;

[0014] Figure 4 The Bi5Ti2O prepared in Example 1 of the present invention 11 XPS spectrum of C1;

[0015] Figure 5 The Bi5Ti2O prepared in Example 1 of the present invention 11 The effect diagram of photocatalytic degradation of Rhodamine B by Cl;

[0016] Figure 6 The Bi5Ti2O prepared in Example 1 of the present invention 11 The effect of Cl photocatalytic oxygen production. DETAILED DESCRIPTION

[0017] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0018] The present invention provides a bismuth titanium oxyhalide material and a preparation method and application thereof, and successfully prepares Bi5Ti2O with a layered structure by a molten salt method. 11X (X is Cl, Br, I) material has the characteristics of large visible light response range, small bandgap width, low photogenerated electron-hole recombination rate, etc. It can be used as a photocatalytic material in the field of pollutant degradation.

[0019] Specifically, according to some embodiments of the present invention, a bismuth titanium oxyhalide material is provided, having the following structural formula: Bi5Ti2O 11 X, wherein x is Cl, Br or I.

[0020] In some embodiments of the present invention, the bismuth titanium oxyhalide material is a Sillén-Aurivillius phase having the following characteristics: Figure 1 The structure shown contains [Bi2O2] 2+ The alternating structure of layers, BiTiO perovskite layers and [C1]-layers has high photostability and visible light response performance.

[0021] According to some embodiments of the present invention, there is also provided a method for preparing the bismuth titanium oxyhalide material as described above, comprising the following steps:

[0022] Bi2O3, TiO2 and BiOX were mixed in a standard stoichiometric ratio, molten salt was added to the mixture, and the mixture was fully ground, and then calcined at 750-900°C for 10-30 hours. The calcined sample was repeatedly washed to remove the molten salt, and the washed sample was dried to obtain Bi5Ti2O 11 X.

[0023] In this step, the standard stoichiometric ratio of Bi2O3, TiO2 and BiOX, that is, the molar ratio of Bi2O3, TiO2 and BiOX is 2:2:1.

[0024] Furthermore, BiOX is a Sillén phase nanosheet, which can be prepared by the following method: according to the standard stoichiometric ratio of potassium halide and bismuth nitrate, potassium bromide aqueous solution is added dropwise to bismuth nitrate alcohol solution and stirred at room temperature, and the solid obtained after stirring is filtered, washed and dried to obtain BiOX nanosheets.

[0025] Furthermore, the molten salt is a mixture of one or more of potassium halide, sodium halide and cesium halide.

[0026] For example, for Bi5Ti2O 11 In the preparation of Cl, the molten salt can be selected from one or more of potassium chloride, sodium chloride and cesium chloride, more specifically, potassium chloride and sodium chloride in a molar ratio of 1:1, but is not limited thereto.

[0027] Furthermore, the addition amount of the molten salt is 50 to 200 mol% of the mixture, for example, it can be 50 mol%, 100 mol%, 150 mol%, 200 mol%, etc.

[0028] More preferably, the calcination temperature is 800° C. and the calcination time is 20 hours, so as to obtain a sample after a single calcination. Optionally, the sample after a single calcination can be repeatedly washed with deionized water or ethanol to remove the molten salt.

[0029] According to some embodiments of the present invention, there is also provided a use of the bismuth titanium oxyhalide material as described above in a photocatalytic material.

[0030] The technical scheme of the present invention is further described below by means of specific examples in combination with the accompanying drawings. It should be noted that the following specific examples are only used as examples, and the protection scope of the present invention is not limited thereto. The chemicals and raw materials used in the following examples are all commercially available or homemade by known preparation methods.

[0031] Example 1

[0032] A method for preparing a bismuth titanium oxychloride compound comprises the following steps:

[0033] Step 1, preparing bismuth oxychloride nanosheets.

[0034] Sub-step 11, weighing 2 mmol of bismuth nitrate pentahydrate, adding it to 20 ml of ethylene glycol, and stirring it with a magnetic stirrer to fully dissolve it, which is recorded as solution A;

[0035] Sub-step 12, weigh 2 mmol of potassium bromide and dissolve it in 10 ml of deionized water, which is referred to as solution B;

[0036] Sub-step 13, adding solution B dropwise into solution A, magnetically stirring at room temperature for 1 hour, then centrifuging and washing, placing the washed sample in an oven at 80° C. to dry, to obtain bismuth oxychloride nanosheets;

[0037] Step 2, preparing bismuth titanium oxychloride compound.

[0038] Sub-step 21, weigh 2 mmol of bismuth trioxide, 1 mmol of bismuth oxychloride obtained in step 1, and 2 mmol of titanium dioxide, and mix them thoroughly; add potassium chloride and sodium chloride (15 mmol each) and grind them thoroughly, then place them in a muffle furnace and calcine them at 800°C for 20 hours; take out the calcined sample, further grind it, and finally wash it repeatedly with deionized water to remove the molten salt, and place the washed sample in an oven to dry to obtain bismuth titanium oxychloride.

[0039] Performance and structural characterization:

[0040] 1. The above bismuth titanium oxychloride compound was tested, and the results were as follows: Figures 2 to 4 As shown, from Figure 2 It can be seen from the XRD spectrum that the diffraction peak is sharp and the crystallinity is high. The synthesized material is Bi5Ti2O 11 Cl. from Figure 3 It can be seen from the SEM spectrum that the synthesized Bi5Ti2O 11 Cl is a flake structure. Figure 4 It can be seen from the XPS spectrum that the synthesized material contains the components of each element in bismuth titanium oxychloride.

[0041] 2. Use the above-mentioned bismuth titanium oxychloride compound to degrade rhodamine B (abbreviated as RhB) under visible light. Specifically, take 100 mg of the ground bismuth titanium oxychloride photocatalytic material, add 100 mL of rhodamine B solution (10 mg / L) and ultrasonicate for 2 minutes (the end of the ultrasonication is recorded as -30 minutes), and stir in a dark room for 30 minutes (the end of the dark reaction is recorded as 0 minutes). Simulate sunlight and irradiate the solution with a xenon lamp. The height of the light source from the upper surface of the solution is 10 cm. Every 15 minutes, take 4 mL of the solution for centrifugation, and measure the absorption spectrum of the centrifuged solution under a UV-visible spectrophotometer. The degradation effect is as follows. Figure 5 As shown, after 90 minutes of illumination, the concentration of Rhodamine B decreased by 100%, that is, it was completely degraded.

[0042] 3. Use the above-mentioned bismuth titanium oxychloride compound to photocatalytically produce oxygen under visible light. Specifically, take 100 mg of the ground bismuth titanium oxychloride photocatalytic material, add 250 mL of a 5 mM AgNO3 aqueous solution, completely remove the air from the reaction system by multiple vacuum pumping before the reaction, simulate sunlight, irradiate the solution with a xenon lamp, and measure the amount of oxygen produced by a gas chromatograph 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, and 5 hours after illumination. The oxygen production effect diagram is as follows Figure 6 As shown, after 5 hours of illumination, the amount of oxygen produced steadily increased, indicating that the above-mentioned bismuth titanium oxychloride compound has good photocatalytic activity and photostability.

[0043] In summary, the preparation process of the present invention is simple, the selected molten salts are all cheap and readily available materials, and are easy to recycle and can be recycled, which is in line with the concept of green development.

[0044] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A bismuth titanium oxyhalide material, characterized in that: Has the following structural formula: Bi5Ti2O 11 X, wherein X is Cl, Br or I, wherein the bismuth titanium oxyhalide material is a Sillén-Aurivillius phase.

2. A method for preparing the bismuth titanium oxyhalide photocatalytic material as claimed in claim 1, comprising the following steps: Bi2O3, TiO2 and BiOX were mixed in a standard stoichiometric ratio, molten salt was added to the mixture, and the mixture was fully ground, and then calcined at 750-900 °C for 10-30 hours. The calcined sample was repeatedly washed to remove the molten salt, and the washed sample was dried to obtain Bi5Ti2O 11 X; the molten salt is a mixture of one or more of potassium halide, sodium halide and cesium halide, and the amount of the molten salt added is 50 to 200 mol% of the mixture.

3. The preparation method according to claim 2, characterized in that: The calcination temperature is 800°C and the calcination time is 20 h.

4. The preparation method according to claim 2, characterized in that: BiOX is a nanosheet of the Sillén phase.

5. The preparation method according to claim 2 or 4, characterized in that: BiOX is prepared by the following steps: According to the standard stoichiometric ratio of potassium halide to bismuth nitrate, the potassium halide aqueous solution is added dropwise to the bismuth nitrate alcohol solution and stirred at room temperature. The solid obtained after stirring is filtered, washed and dried to obtain BiOX nanosheets.

6. Use of the bismuth titanium oxyhalide material as claimed in claim 1 in photocatalytic materials.

Images