P-doped BiOCl visible-light-driven photocatalyst and preparation method thereof

文档序号：838088 发布日期：2021-04-02 浏览：30次中文

阅读说明：本技术 一种P掺杂BiOCl可见光催化剂及其制备方法 (P-doped BiOCl visible-light-driven photocatalyst and preparation method thereof ) 是由岑望来曹晋妍刘勇军楚英豪李建军于 2020-12-30 设计创作，主要内容包括：本发明提供一种P掺杂BiOCl可见光催化剂及其制备方法,该方法通过将硝酸铋悬浮液与氯化钾溶液混合,并添加磷源后,调节混合溶液的pH至2.5～3.5作为反应液,于160℃～180℃下反应20h～24h制得,其中磷源为H-3PO-4、NaH-2PO-2·H-2O、NaH-2PO-4和Na-3PO-4其中任意一种。本发明通过选择限定的掺杂磷源以及掺杂配比,采用一步水热法合成制备了P掺杂BiOCl可见光催化剂,该催化剂的可见光活性可达BiOCl光催化剂的2.73倍,其制备方法工艺简单,具有极佳的应用前景。(The invention provides a P-doped BiOCl visible-light-induced photocatalyst and a preparation method thereof, and the P-doped BiOCl visible-light-induced photocatalyst is prepared by mixing a bismuth nitrate suspension with a potassium chloride solution, adding a phosphorus source, adjusting the pH of the mixed solution to 2.5-3.5 to serve as a reaction solution, and reacting at 160-180 ℃ for 20-24H to obtain the P-doped BiOCl visible-light-induced photocatalyst, wherein the phosphorus source is H 3 PO 4 、NaH 2 PO 2 ·H 2 O、NaH 2 PO 4 And Na 3 PO 4 Any one of them. The invention is provided withThe P-doped BiOCl visible light catalyst is prepared by selecting a limited doped phosphorus source and a doping proportion and adopting a one-step hydrothermal method, the visible light activity of the catalyst can reach 2.73 times that of the BiOCl photocatalyst, and the preparation method has a simple process and excellent application prospect.)

1. A preparation method of a P-doped BiOCl visible light catalyst is characterized by comprising the following steps of:

(1) adding Bi (NO)₃)₃·5H₂Adding O into ethylene glycol, and fully stirring to obtain bismuth nitrate suspension; adding KCl into deionized water, and stirring to dissolve to obtain a potassium chloride solution;

(2) mixing the bismuth nitrate suspension obtained in the step (1) with a potassium chloride solution, adding a phosphorus source, adjusting the pH value of the mixed solution to 2.5-3.5, stirring for at least 30min until the pH value of the solution is not changed, and taking the solution as a reaction solution; wherein the addition amount of the phosphorus source is Bi (NO) based on the molar weight of the phosphorus element₃)₃·5H₂O：P＝(6～40)：1；

Wherein the phosphorus source is H₃PO₄、NaH₂PO₂·H₂O、NaH₂PO₄And Na₃PO₄Any one of them;

(3) and (3) reacting the reaction liquid obtained in the step (2) at 160-180 ℃ for 20-24 h, cooling, washing and drying to obtain the P-doped BiOCl visible light catalyst.

2. The method of claim 1, wherein: bi (NO) in the step (1)₃)₃·5H₂The molar ratio of O to KCl is (0.8-1.2): 1.

3. The method of claim 1, wherein: in the step (1), the concentration of the bismuth nitrate suspension is 5-5.2 wt%, and the concentration of the potassium chloride solution is 3.5-3.6 wt%.

4. The method of claim 1, wherein: in the step (2), the phosphorus source is NaH₂PO₂·H₂O。

5. The method of claim 1, wherein: in the step (2), the addition amount of the phosphorus source is based on the molar weight of the phosphorus element, and Bi (NO)₃)₃·5H₂O：P＝(6～30)：1。

6. The method of claim 1, wherein: in the step (2), the addition amount of the phosphorus source is based on the molar weight of the phosphorus element, and Bi (NO)₃)₃·5H₂O：P＝(8～20)：1。

7. The method of claim 1, wherein: in the step (2), the addition amount of the phosphorus source is based on the molar weight of the phosphorus element, and Bi (NO)₃)₃·5H₂O：P＝10：1。

8. The P-doped BiOCl visible light catalyst prepared by the preparation method of any one of claims 1 to 7.

Technical Field

The invention belongs to the technical field of preparation of visible light catalytic materials, and particularly relates to a P-doped BiOCl visible light catalyst and a preparation method thereof, which are mainly applied to the technical direction of water treatment in the field of environmental protection.

Background

Energy and environmental issues are two major challenges facing the current sustainable development of human society. The sunlight is used as an energy source, and environmental pollutants are removed by a photocatalysis method, so that the method is expected to become an important technology for meeting challenges. The core of the photocatalytic technology is a photocatalyst. Bismuth oxychloride (BiOCl) is a group of compounds consisting of [ Bi₂O₂]²⁺Layer and Cl^-The photocatalyst formed by the alternate arrangement of the layers has wide sources and low price, has proper forbidden bandwidth and good stability, is easy to modify and receives wide attention.

However, BiOCl is an ultraviolet light response type photocatalyst, so that the utilization rate of visible light is low, and the requirement of practical application is difficult to meet. Therefore, it is highly desirable to develop a highly efficient photocatalytic material having a visible light response.

The existing research shows that the optical response range of the semiconductor material can be expanded by properly doping the semiconductor material, and the carrier separation efficiency is improved, so that the photocatalytic activity of the semiconductor material is improved. In the existing literature reports, researchers mostly concentrate on doping rare earth metal elements or nonmetal elements such as N, C, S in the preparation process of BiOCl to improve the photocatalytic performance of the BiOCl, for example, in research on preparation, modification and photocatalytic performance of bismuth oxychloride (xu xiang, jilin university 2016 (thesis of great university of jilin), graphene is doped in the preparation process of BiOCl, so that the photocatalytic performance of the prepared material is improved.

However, until now, no reports have been made in China on the relevant research of improving the photocatalytic performance by doping BiOCl with P. It is not clear to the skilled artisan whether P-doped BiOCl can improve the catalytic performance and the magnitude of the increase in BiOCl.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a P-doped BiOCl visible-light-driven photocatalyst and a preparation method thereof, the P-doped BiOCl visible-light-driven photocatalyst is prepared by selecting a limited doped phosphorus source and a doping proportion and adopting a one-step hydrothermal method, the visible light activity of the catalyst can reach 2.73 times that of the BiOCl photocatalyst, and the preparation method has a simple process and has an excellent application prospect.

In order to achieve the purpose, the invention adopts the technical scheme formed by the following technical measures.

A preparation method of a P-doped BiOCl visible light catalyst comprises the following steps of:

Wherein the phosphorus source is H₃PO₄、NaH₂PO₂·H₂O、NaH₂PO₄And Na₃PO₄Any one of them;

(3) and (3) reacting the reaction liquid obtained in the step (2) at 160-180 ℃ for 20-24 h, cooling, washing and drying to obtain the P-doped BiOCl visible light catalyst.

In general, Bi (NO) in the step (1)₃)₃·5H₂The proportion of O and KCl is consistent with the technical scheme of preparing BiOCl by a hydrothermal method in the prior art, and the technical personnel in the field can refer to the technical documents related to the preparation of BiOCl by the hydrothermal method of bismuth nitrate pentahydrate and potassium chloride. For a better illustration of the invention, and provideA reference solution is provided, wherein in the step (1), Bi (NO) is provided₃)₃·5H₂The molar ratio of O to KCl is (0.8-1.2): 1.

In addition, regarding the concentrations of the bismuth nitrate suspension and the potassium chloride solution in the step (1), the skilled person can refer to the technical literature relating to the preparation of BiOCl by hydrothermal method of bismuth nitrate pentahydrate and potassium chloride. In order to better illustrate the invention and provide a referable technical scheme, the concentration of the bismuth nitrate suspension in the step (1) is 5-5.2 wt%, and the concentration of the potassium chloride solution is 3.5-3.6 wt%.

It is worth noting that in the experimental process, the inventor of the present invention found that, after the phosphorus source is added in step (2), the pH of the mixed solution needs to be adjusted to 2.5-3.5, because based on experimental facts, the solution peracid affects the material crystallization when the pH of the mixed solution is lower than 2.5; when the pH value of the mixed solution is higher than 6.5, the phosphorus element is easy to form bismuth phosphate and form a heterojunction with bismuth oxychloride, and the photocatalytic activity of the mixed solution is greatly inferior to that of phosphorus-doped bismuth oxychloride.

It is worth to be emphasized that, in the further experimental process, the inventors of the present invention found that, although the pH of the mixed solution is adjusted to 2.5-6.5 in the step (2), successful preparation of the P-doped BiOCl visible light photocatalyst can be satisfied. However, a control experiment shows that when the pH of the mixed solution is adjusted to 4.0-6.5, the visible light activity of the prepared P-doped BiOCl visible light catalyst is not obviously improved in a test compared with that of the BiOCl visible light catalyst; and when the pH value of the mixed solution is adjusted to 2.5-3.5, the visible light activity of the prepared P-doped BiOCl visible light catalyst can reach 2.73 times that of the BiOCl visible light catalyst in a test. At present, the inventor of the present invention has not found or speculated the reason why such a huge difference in visible light activity occurs in adjusting the pH value of the mixed solution, so that the present invention only protects the process scheme with a great improvement in the photocatalytic performance thereof due to the scientific attitude of the fact, and limits the adjustment of the pH of the mixed solution in the step (2) to 2.5-3.5.

Wherein, in the step (1), Bi (NO) is used₃)₃·5H₂O adding ethylene glycolFully stirring in alcohol to obtain bismuth nitrate suspension, generally stirring to obtain bismuth nitrate white suspension; the KCl is added into deionized water, stirred and dissolved to obtain a potassium chloride solution, and usually stirred and dissolved to obtain a transparent potassium chloride solution. A person skilled in the art can select a proper stirring mode and time by himself or herself on the basis of achieving the configuration purpose according to the actual addition amount of the materials and referring to the prior art. To better illustrate the invention and to provide a reference solution, the Bi (NO) is described under laboratory conditions₃)₃·5H₂And when the addition amount of O is 4.85g and the amount of ethylene glycol is 50ml, mechanically stirring for 30min at 100r/min to obtain a bismuth nitrate suspension, wherein the addition amount of KCl is 0.75g and the amount of deionized water is 50ml, and mechanically stirring for 5min at 100r/min to obtain a potassium chloride solution.

Wherein, in the step (3), the reaction solution obtained in the step (2) is reacted for 20 to 24 hours at 160 to 180 ℃, and then a light gray precipitate with slow sedimentation rate is formed, but the above conditions are limited under laboratory conditions, and those skilled in the art can select appropriate reaction temperature and reaction time according to actual industrialized production conditions.

It is worth further explaining that, in the development process of the technical scheme of the present invention, the inventors found that the selection and doping ratio of the doped phosphorus source greatly affect the photocatalytic performance of the finally prepared P-doped BiOCl visible-light-induced photocatalyst.

Wherein, through the control test, the phosphorus source is considered to be selected as H₃PO₄、NaH₂PO₂·H₂O、NaH₂PO₄And Na₃PO₄In any case, the prepared P-doped BiOCl visible-light-driven photocatalyst shows a photocatalytic performance which is greatly higher than that of the original BiOCl visible-light-driven photocatalyst, so that the selection of the phosphorus source is limited by the invention due to the attitude of practical matters.

Further through a control experiment, the selection of the phosphorus source influences the catalytic performance of the doped catalyst to be sequenced, and NaH₂PO₂·H₂O＞Na₃PO₄＞NaH₂PO₄＞H₃PO₄Wherein NaH is added₂PO₂·H₂O is used as a doped phosphorus source, and the visible light activity of the O is H under the condition of consistent other conditions₃PO₄1.49 times of the doped phosphorus source.

Wherein, through a control test, the Bi (NO) is considered to satisfy the step (2)₃)₃·5H₂O: p ═ 6-40): 1, the prepared P-doped BiOCl visible light catalyst has visible light activity at least 1.64 times that of the BiOCl photocatalytic material by using a tetracycline solution in a xenon lamp degradation test.

In order to further improve the photocatalytic performance of the prepared P-doped BiOCl visible-light-induced photocatalyst, Bi (NO) is added in the step (2)₃)₃·5H₂O: p ═ 6-30): under the condition, the prepared P-doped BiOCl visible light catalyst has visible light activity at least 2.10 times that of a BiOCl photocatalytic material by using a tetracycline solution in a xenon lamp degradation test.

In order to further obtain a P-doped BiOCl visible light photocatalyst having a visible light activity at least 2.40 times that of the BiOCl photocatalytic material, said Bi (NO) in step (2)₃)₃·5H₂O: p ═ 8-20): 1. when said Bi (NO) is in step (2)₃)₃·5H₂O: p is 10: 1, the visible light activity is 2.73 times that of the BiOCl photocatalytic material, and the excellent photocatalytic performance is shown.

After the invention is finished, the inventor adopts a tetracycline solution with the concentration of 20mg/L as a degradation object to test the photocatalytic performance of the P-doped BiOCl visible-light-driven photocatalyst provided by the invention. 50mg of the photocatalyst provided by the invention is put into 100mL of tetracycline solution, and after adsorption for 30min under a dark condition, the mixed reaction solution is transferred into a circulating water reaction tank for photocatalytic reaction. The reaction light source was a 300W xenon lamp equipped with a 420nm filter. 1mL of tetracycline reaction solution was collected every 2.5min, filtered through a filter head, and then the tetracycline concentration was measured by liquid chromatography. Test results show that the visible light activity of the P-doped BiOCl visible light catalyst provided by the invention can reach 2.73 times of that of a BiOCl photocatalytic material. The specific experimental results are shown in the attached drawings of the specification.

The invention has the following beneficial effects:

(1) the P-doped BiOCl visible light catalyst is prepared by selecting a limited doped phosphorus source and a limited doping proportion and adopting a one-step hydrothermal method, and the visible light activity of the catalyst can reach 2.73 times that of the BiOCl photocatalyst;

(2) the invention researches a specific process for doping non-metal ions P into the BiOCl structure, finds that the pH value in the process condition greatly influences whether the P-doped BiOCl visible-light-driven photocatalyst is successfully prepared or not, and the prepared P-doped BiOCl visible-light-driven photocatalyst only shows excellent photocatalytic performance when the pH value is within the limited range of the invention;

(3) the invention has the advantages of few raw material types, low price, easy obtaining, mild reaction conditions, simple preparation process and low requirement on equipment; the non-metal ions P are doped into the BiOCl structure, so that the energy band structure and the forbidden bandwidth of the BiOCl photocatalytic material are changed, the visible light absorption range of the BiOCl photocatalytic material is greatly enlarged, and the BiOCl photocatalytic material has a good application prospect.

Drawings

Figure 1 is an X-ray diffraction (XRD) pattern of the P-doped raw BiOCl visible-light photocatalyst of comparative example 1, which is not doped with P, and the P-doped BiOCl visible-light photocatalyst prepared in example 1 according to the present invention. As can be seen by comparing with the standard card, the diffraction peak of P-BiOCl in the figure is consistent with the standard spectrum of BiOCl (JCPDS51-0939), and no other impurity phase exists, which indicates that the introduction of P does not change the crystal phase of BiOCl. The diffraction peak in the XRD small graph is shifted to a low-angle direction, and the fact that P replaces Cl to enter the BiOCl crystal lattice is proved.

FIG. 2 is a Scanning Electron Microscope (SEM) image of a P-doped BiOCl visible light photocatalyst prepared in example 1 of the present invention. It can be obviously seen that the prepared P-doped BiOCl visible-light-driven photocatalyst is of a sheet-like structure.

FIG. 3 is a transmission electron microscopy mapping image of the P-doped BiOCl visible-light-driven photocatalyst prepared in example 1. The upper left is shot in HAADF mode, the upper right is Si element, the middle left is Cl element, the middle right is O element, and the lower is P element. Obviously, four elements of Bi, O, Cl and P are uniformly distributed in the material.

Fig. 4 is a graph of the uv-vis diffuse reflectance spectra of the P-doped BiOCl visible photocatalyst of comparative example 1, which is not doped with P, and the P-doped BiOCl visible photocatalyst prepared in example 1 according to the present invention. It can be obviously seen that the P-doped BiOCl visible light catalyst has a wider photoresponse range than a single BiOCl photocatalytic material, and the absorption of visible light is obviously enhanced.

Fig. 5 is a graph of the fluorescence spectra of the P-doped raw BiOCl visible-light photocatalyst of comparative example 1, which is not doped with P, and the P-doped BiOCl visible-light photocatalyst prepared in example 1 according to the present invention. Obviously, the recombination rate of the photon-generated carriers of the P-doped BiOCl visible-light-induced photocatalyst is lower than that of a single BiOCl photocatalytic material, which shows that the separation efficiency of the photon-generated carriers is improved by doping P.

FIG. 6 is a graph showing the comparison of the activity of the P-undoped BiOCl visible photocatalyst of comparative example 1 and the activity of the P-doped BiOCl visible photocatalyst prepared in example 1 of the present invention in degrading 20mg/L tetracycline solution by photocatalysis in visible light. The comparison shows that the photocatalytic activity of the P-doped BiOCl visible-light-induced photocatalyst is obviously higher than that of a single BiOCl material, and the photocatalytic rate of the P-doped BiOCl visible-light-induced photocatalyst is 2.73 times that of the BiOCl material.

FIG. 7 is a comparison graph of the activity of P-doped BiOCl visible-light-induced photocatalyst prepared in examples 1-6 of the present invention and the activity of P-undoped original BiOCl visible-light-induced photocatalyst prepared in comparative example 1 for photocatalytic degradation of 20mg/L tetracycline solution under visible light.

FIG. 8 is a comparison graph of the activity of a P-doped BiOCl visible-light-induced photocatalyst prepared in examples 1 and 7-9 of the present invention and the activity of an original P-undoped BiOCl visible-light-induced photocatalyst prepared in comparative example 1 for photocatalytic degradation of a 20mg/L tetracycline solution under visible light.

Detailed Description

The invention is further illustrated by the following examples in conjunction with the accompanying drawings. It should be noted that the examples given are not to be construed as limiting the scope of the invention, and that those skilled in the art, on the basis of the teachings of the present invention, will be able to make numerous insubstantial modifications and adaptations of the invention without departing from its scope.

The following examples, which use tetracycline solution with concentration of 20mg/L as degradation object, were used to test the photocatalytic performance of the P-doped BiOCl visible-light-driven photocatalyst provided in the examples. 50mg of the photocatalyst prepared in example was put into 100mL of a tetracycline solution, adsorbed in the dark for 30min, and then the mixed reaction solution was transferred to a circulating water reaction tank for photocatalytic reaction. The reaction light source was a 300W xenon lamp equipped with a 420nm filter. 1mL of tetracycline reaction solution was collected every 2.5min, filtered through a filter head, and then the tetracycline concentration was measured by liquid chromatography.

Example 1