Preparation method and application of boron-nitrogen-doped strontium titanate

Abstract

The invention discloses a preparation method and application of boron-nitrogen-doped strontium titanate. The preparation method comprises the following steps: preparing a precursor I boron-doped titanium dioxide from hydrothermal TiB2; mixing the precursor I with strontium carbonate, and calcining at high temperature to prepare boron-doped SrTiO3; and then nitriding to obtain the boron-nitrogen-doped SrTiO3. The precursor I and strontium carbonate are mixed and then calcined at high temperature to synthesize boron-doped strontium titanate, the boron-nitrogen co-doped strontium titanate can be prepared by nitriding in ammonia gas flow, and the boron-nitrogen co-doped strontium titanate shows corresponding activity in the field of photocatalytic pollutant degradation.

Description

Technical Field

[0001] The invention belongs to the technical field of material synthesis and pollutant degradation, and specifically relates to a preparation method of boron-nitrogen doped strontium titanate and application thereof. Background Art

[0002] Strontium titanate is a star material in the field of photocatalysts, but its absorption spectrum is mainly in the ultraviolet region, which limits its application. The means to expand the absorption spectrum of semiconductor photocatalytic materials include doping with cations, doping with anions, forming solid solutions, and surface disordering. A lot of work has been done on the modification of strontium titanate. Cation doping can form localized energy levels, and typical examples include SrTiO 3 :Cr、SrTiO 3 :Rh, etc. Doping can reduce the bandgap width of the material and expand the light absorption range of the material, but doping is easy to form a recombination center of electrons and holes, affecting charge separation. By doping with two metals, the charge balance can be compensated and the formation of recombination centers can be suppressed. Typical examples include SrTiO 3 :La / Rh、SrTiO 3 :Bi / Rh, etc. Anion doping is mainly non-metallic ion doping, mainly SrTiO 3 -xNx、SrTiO 3-3 / 2x-1 / 2y N x H y wait.

[0003] Taking titanium dioxide as an example, the methods of uniform nitrogen doping mainly include the following two points: (1) using the inherent channels in the layered or tunnel-like structured oxides to achieve uniform doping from the surface to the bulk. In 2008, Professor Liu Gang's research group reported the uniform nitrogen doping of layered titanate Cs 0.68 Ti 1.83 O 4 , Cs can be obtained by nitridation in ammonia 0.68 Ti 1.83 O 4-x N x , making full use of the titanate layered structure to achieve uniform doping of nitrogen atoms, and the absorption spectrum expanded from 356nm to 472nm; (2) by weakening the titanium-oxygen bond to reduce the energy required for nitrogen atoms to replace oxygen atoms, high-concentration bulk phase doping was achieved. In 2012, Professor Liu Gang's research group reported gradient boron-nitrogen co-doped red titanium dioxide. The method was to hydrolyze titanium boride by hydrothermal method, pre-dope boron atoms into titanium dioxide, weaken the titanium-oxygen bond in titanium dioxide, and make it easier for nitrogen atoms to replace oxygen atoms. Its absorption spectrum can reach 700nm, and there is no Ti 3+ Considering the existence of SrTiO 3 The structure of SrTiO 3-xN x Nitrogen doping is concentrated on the surface and it is impossible to achieve uniform doping in the bulk phase. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing boron-nitrogen doped strontium titanate.

[0007] In order to solve the above technical problems, the present invention provides the following technical solution: a method for preparing boron-nitrogen-doped strontium titanate, characterized in that: comprising:

[0008] Preparation of boron-doped titanium dioxide, denoted as precursor Ⅰ;

[0009] The precursor I and strontium carbonate are calcined at high temperature to obtain boron-doped strontium titanate, which is recorded as precursor II;

[0010] The precursor II is nitrided in an ammonia stream to obtain boron-nitrogen doped strontium titanate.

[0011] As a preferred embodiment of the preparation method of the present invention, the boron-doped titanium dioxide is prepared by hydrothermally preparing titanium dioxide in a mixed solution.

[0012] As a preferred embodiment of the preparation method of the present invention, the mixed solution is 1M HCl and 0.1M Na 2 SO 4 of mixed solution.

[0013] As a preferred embodiment of the preparation method of the present invention, the hydrothermal temperature is 180-200° C. and the time is 6-24 hours.

[0014] As a preferred embodiment of the preparation method of the present invention, the precursor I and strontium carbonate are calcined at high temperature, wherein the calcination temperature is 900-1100° C. and the calcination time is 4-8 hours.

[0015] As a preferred embodiment of the preparation method of the present invention, the precursor II is nitrided in an ammonia gas flow, wherein the nitridation condition is an ammonia gas flow of 100 to 250 mL / min.

[0016] As a preferred embodiment of the preparation method of the present invention, the nitriding temperature is 500-600° C. and the nitriding time is 1-2 hours.

[0017] Another object of the present invention is to overcome the deficiencies in the prior art and provide a boron-nitrogen doped strontium titanate.

[0018] Another object of the present invention is to overcome the deficiencies in the prior art and provide a method for using boron-nitrogen doped strontium titanate in photocatalytic degradation of pollutants.

[0019] As a preferred embodiment of the application of the present invention, the boron and nitrogen doped strontium titanate can be used to degrade the carcinogen rhodamine B under visible light.

[0020] Beneficial effects of the present invention:

[0021] The present invention prepares boron-doped strontium titanate by mixing precursor I with strontium carbonate and calcining at high temperature, and then nitriding in an ammonia gas flow to prepare boron-nitrogen co-doped strontium titanate, which exhibits corresponding activity in the photocatalytic pollutant degradation reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0023] Figure 1 A flow chart is prepared for an embodiment of the present invention.

[0024] Figure 2 1 and 1 are XRD diagrams of Example 1 (boron and nitrogen doped strontium titanate) of the present invention and Comparative Example 1 (nitrogen doped strontium titanate).

[0025] Figure 3 The UV-vis graphs of Example 1 (boron and nitrogen doped strontium titanate) of the present invention and Comparative Example 1 (nitrogen doped strontium titanate) are shown.

[0026] Figure 4 The photocatalytic degradation activity diagram of pollutants of Example 1 (boron and nitrogen doped strontium titanate) of the present invention and Comparative Example 1 (nitrogen doped strontium titanate) is shown. DETAILED DESCRIPTION

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0028] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0029] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0030] The raw materials used in the present invention are: titanium boride, Sigma-Aldrich; HCl solution, Sinopharm Chemical Reagent Co., Ltd.; sodium sulfate, Sinopharm Chemical Reagent Co., Ltd.; and strontium carbonate, Sinopharm Chemical Reagent Co., Ltd.

[0031] Instruments used in the embodiments of the present invention:

[0032] XRD: Rigaku D / Max-2500 X-ray diffractometer from Rigaku Corporation;

[0033] UV-Vis DRS: JASCO V-550 spectrometer;

[0034] Liquid phase degradation light absorption intensity was calculated by C / Co: Varian Cary 50Uv-vis spectrometer.

[0035] Example 1

[0036] This embodiment discloses a method for preparing boron-nitrogen co-doped strontium titanate, such as Figure 1 As shown, first synthesize B-doped titanium dioxide, mix it with strontium carbonate and grind it, and then calcine it at high temperature in air to synthesize B-doped strontium titanate, and then nitride it in an ammonia stream to obtain boron-nitrogen co-doped strontium titanate. The method mainly includes the following steps:

[0037] (1) Preparation of Precursor I (B-doped Titanium Dioxide)

[0038] Take 0.1g TiB 2 Add 60 mL of 1M HCl and 0.1M Na 2 SO 4 The mixed solution was stirred for half an hour and placed in a hydrothermal reactor for hydrothermal reaction at a reaction temperature of 180°C and a hydrothermal time of 4 hours.

[0039] (2) Preparation of Precursor II (B-doped SrTiO3)

[0040] The precursor I (B-doped titanium dioxide) was cooled and centrifuged, ground with strontium carbonate, and calcined at high temperature in air, calcined in a muffle furnace at 1000°C for 6 hours.

[0041] (3) Preparation of boron-nitrogen doped strontium titanate

[0042] Precursor II was nitrided in an ammonia gas flow of 250 mL / min, the nitriding temperature was 600°C, and the nitriding time was 2 h.

[0043] Comparative Example 1

[0044] In this comparative example, titanium dioxide and strontium carbonate are directly mixed and ground, calcined at high temperature, and then nitrided in an ammonia stream to obtain boron-nitrogen co-doped strontium titanate. The method mainly includes the following steps:

[0045] (1) Preparation of strontium titanate

[0046] Titanium dioxide and strontium carbonate are directly mixed and ground in a molar ratio of 1:1, and calcined at high temperature in air to obtain strontium titanate. The calcination temperature is 1100° C. and the calcination time is 6 hours.

[0047] (2) Preparation of nitrogen-doped strontium titanate

[0048] The nitridation was carried out in an ammonia gas flow of 250 mL / min, the nitridation temperature was 600° C., and the nitridation time was 2 h.

[0049] Figure 2 , 3 They are XRD graphs and UV-vis graphs of Example 1 (boron and nitrogen doped strontium titanate) of the present invention and Comparative Example 1 (nitrogen doped strontium titanate), respectively.

[0050] Example 2

[0051] This example is an activity evaluation experiment of photocatalytic pollutant degradation using Example 1 (boron and nitrogen doped strontium titanate) and Comparative Example 1 (nitrogen doped strontium titanate) as photocatalysts. The reaction conditions are: 75 mg strontium titanate sample, 150 mL RhB solution, and the solution concentration is 1×10 -5 mol / L; 300W xenon lamp light source. Specifically include:

[0052] The experiment of strontium titanate degradation of liquid RhB was carried out in an intermittent reaction device. The reactor was a Pyrex glass reactor, and the temperature of the reaction system was maintained at room temperature by a condensing water jacket. An infrared filter filled with water was used above the reactor to absorb and filter out the infrared part of the light source, so that the reaction liquid would not absorb infrared light and heat up. The reaction light source was a Japanese xenon lamp light source (model LX 300F, power 300W, equipped with L-42 filter, λ ≥ 420nm). Before the reaction, 150mL of RhB solution was added to the reactor, and then 75mg of strontium titanate sample was added. Stir in the dark for 2h to ensure that RhB established adsorption and desorption equilibrium on the surface of the strontium titanate photocatalyst. Turn on the light source for photocatalytic reaction, take about 5.0mL of reaction solution every 15min, and take the reaction solution taken at different times after centrifugation, and take the supernatant for testing on a Varian Cary 50Uv-vis spectrometer. The conversion rate of strontium titanate photocatalytic degradation of liquid RhB was measured by C / C 0 Calculated, where C 0 is the initial concentration of RhB at adsorption-desorption equilibrium, and C is the concentration of RhB in the supernatant sampled at different times. When other conditions are constant, the concentration of the dye solution is proportional to its light absorption intensity, corresponding to the peak intensity at the maximum absorption peak of the dye, and the final degradation rate is equal to (1-C / C 0 )×100%. The maximum absorption peak of RhB is located at 554nm. The evaluation results of the activity evaluation experiment of photocatalytic pollutant degradation are as follows Figure 4 shown.

[0053] Example 3

[0054] The difference between this embodiment and embodiment 1 is that the hydrothermal time in step (1) is replaced with 24 hours, and the remaining steps are the same as those in embodiment 1.

[0055] Example 4

[0056] The difference between this embodiment and embodiment 1 is that strontium nitrate in step (2) is replaced by strontium carbonate, the calcination temperature is replaced by 1000° C., and the remaining steps are the same as those in embodiment 1.

[0057] Comparative Example 2

[0058] The difference between this comparative example and Example 1 is that the titanium dioxide in step (1) is replaced by boron-doped titanium dioxide, step (2) is cancelled, and the remaining steps are the same as those in Example 1.

[0059] The materials prepared in Examples 1, 3, 4 and Comparative Example 2 were used as photocatalysts to conduct an activity evaluation experiment for photocatalytic pollutant degradation. The evaluation method was the same as that in Example 2. The evaluation results are shown in Table 1.

[0060] Table 1

[0061] <h2 style=";text-align:left;direction:ltr"><![CDATA[C / C <h2 style=";text-align:left;direction:ltr"> 0 <h2 style=";text-align:left;direction:ltr"> (90 min)]]><h2 style=";text-align:left;direction:ltr"> Example 1 0.67 Example 3 0.75 Example 4 0.80 Comparative Example 1 0.88 Comparative Example 2 0.84

[0062] The key to Example 1 is to retain as much boron as possible. During the hydrothermal synthesis of B-doped titanium dioxide, B is in the negative valence state. n- In the presence of heating, SrTiO is synthesized 3 In this process, B is oxidized to form B n+ , which can promote N-doping during the nitridation process. The difference in Example 3 is that the hydrothermal process is too long, and the synthesized B-doped titanium dioxide particles are very large, which is not conducive to subsequent nitrogen doping. The difference in Example 4 is that strontium carbonate is used to synthesize B-doped titanium dioxide. The melting point of strontium carbonate is higher than that of strontium nitrate, which causes the volatilization of boron element, which is not conducive to subsequent nitrogen doping. Comparative Example 2 proves that boron-doped titanium dioxide has poor activity without nitrogen doping. According to the conditions of Comparative Examples 1 and 2, strontium titanate is basically not nitrided, and the starting temperature of nitridation is 550°C. The strontium titanate perovskite structure is not easily nitrided, so it has no obvious light absorption peak in the visible light region (such as Figure 3 ).

[0063] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the present invention.

Claims

1. A method for preparing boron-nitrogen doped strontium titanate, characterized in that: include, Preparation of boron-doped titanium dioxide, denoted as precursor Ⅰ; The precursor I and strontium carbonate are calcined at high temperature to obtain boron-doped strontium titanate, which is recorded as precursor II; The precursor II is nitrided in an ammonia stream to obtain boron-nitrogen doped strontium titanate.

2. The preparation method according to claim 1, characterized in that: The boron-doped titanium dioxide is prepared by hydrothermally preparing the titanium dioxide in a mixed solution.

3. The preparation method according to claim 2, characterized in that: The mixed solution is a mixed solution of 1M HCl and 0.1M Na2SO4.

4. The preparation method according to claim 2, characterized in that: The hydrothermal temperature is 180-200° C. and the time is 6-24 hours.

5. The preparation method according to claim 1, characterized in that: The precursor I and strontium carbonate are calcined at high temperature, wherein the calcination temperature is 900-1100° C. and the calcination time is 4-8 hours.

6. The preparation method according to claim 1, characterized in that: The precursor II is nitrided in an ammonia gas flow, wherein the nitriding condition is an ammonia gas flow of 100 to 250 mL / min.

7. The preparation method according to claim 6, characterized in that: The nitriding temperature is 500-600° C., and the nitriding time is 1-2 hours.

8. Boron-nitrogen doped strontium titanate obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the boron and nitrogen doped strontium titanate as claimed in claim 8 in photocatalytic degradation of pollutants.

10. The use according to claim 9, characterized in that: The boron and nitrogen doped strontium titanate can be used to degrade the carcinogen rhodamine B under visible light.

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