CN113209993A

CN113209993A - Preparation method of La-doped petal-shaped BiOBr photocatalytic material

Info

Publication number: CN113209993A
Application number: CN202110518522.0A
Authority: CN
Inventors: 杨树龙; 戴子阳; 魏政清; 陈祖生; 佟煜轩; 翁臻; 周祺琳; 谢宇
Original assignee: Nanchang Hangkong University
Current assignee: Nanchang Hangkong University
Priority date: 2021-05-12
Filing date: 2021-05-12
Publication date: 2021-08-06

Abstract

The invention provides a method for preparing a BiOBr/La photocatalyst material by solvothermal synthesis. The method has stronger absorption capacity in a visible light region, the band gap energy becomes smaller, the electron transition is facilitated, the electron-hole pair separation efficiency is higher, and lanthanum has the advantages of small radius, low price and higher affinity to oxygen, so that the lanthanum has wide application prospects in the aspects of pollutant degradation and new energy development by utilizing solar energy.

Description

Preparation method of La-doped petal-shaped BiOBr photocatalytic material

Technical Field

The invention discloses a rare earth La-doped flower-shaped BiOBr nanosheet composite material prepared by a solvothermal synthesis method, and particularly belongs to the field of preparation of photocatalytic materials.

Background

With the development of society and economy, carbon dioxide emission has attracted wide attention of people in all communities. The rising carbon dioxide content of the atmosphere is one of the main causes of global warming. Due to the rapid development of industrialization and urbanization, excessive dependence on and consumption of fossil fuels are important causes of a sharp rise in the carbon dioxide content in the atmosphere.

BiOBr is a semiconductor material with narrow band gap energy, the band gap energy of which is between 2.4-2.7eV, and the narrower band gap energy enables the semiconductor material to respond to visible light, and most importantly, the semiconductor material can reduce carbon dioxide into hydrocarbon fuel. Simple BiOBr has lower quantum efficiency, and in order to improve the photocatalytic efficiency of the BiOBr, methods of photocatalyst loading, morphology regulation, metal deposition, chemical defect formation and the like have been proposed.

Elemental doping is considered to be an effective method for improving the catalytic performance of the catalyst. Lanthanum in the rare earth metal elements has the advantages of small radius, low price and high affinity to oxygen. Recently, doping of the catalyst with a rare earth element has been shown to be effective in inhibiting the separation of electron-hole pairs. This is because it has abundant energy levels, special optical properties and 4f electron transition characteristics.

Disclosure of Invention

The invention provides a method for preparing a La-doped petal-shaped BiOBr photocatalytic material by solvothermal synthesis, which comprises the following steps of:

(1) cetyl trimethylammonium bromide (CTAB) was dispersed in a beaker containing Ethylene Glycol (EG) solvent and stirred by a magnetic stirrer for 30 minutes to form a white emulsion as solution a.

(2) Mixing the hydrated lanthanum nitrate solution and the pentahydrated bismuth nitrate solution, and stirring for 30 minutes to obtain a solution B; solution B was poured into solution a and sonicated for 10 minutes.

(3) Transferring the suspension obtained in the step (2) into a reaction kettle, and reacting at 160 ℃ for 12 hours.

(4) After the reaction in step (3) was completed, the precipitate was separated, washed and dried, and the obtained sample was named as BiOBr/La-x% (x represents a molar ratio of the La element and the Bi element incorporated, and x is 0, 1.6, 4.9, 8.1).

Preferably, in step (1), the mass of the hexaalkyltrimethylammonium bromide is 1.0933 g.

Preferably, in the step (2), the mass of the hydrated lanthanum nitrate is 0g, 0.016g, 0.048g and 0.0795g respectively, and the mass of the pentahydrated bismuth nitrate is 1.4552 g.

Preferably, in step (3), the inner lining of the reaction kettle is made of polytetrafluoroethylene.

Preferably, the molar ratio of the La element to the Bi element is 0, 1.6%, 4.9%, or 8.1% in theory.

The La-doped petal-shaped BiOBr photocatalytic material obtained by the method can be used for reducing carbon dioxide, and the CO2 conversion efficiency can be greatly improved under the irradiation of sunlight only by directly putting the prepared BiOBr/La photocatalytic material into a system of carbon dioxide gas.

The La3+ is successfully doped on the BiOBr nano-chip by a simple hydrothermal synthesis method. From the results, only the diffraction peak of BiOBr was found, and no peak of other phase (for example, La2O3 or La (oh)3) was observed, indicating that La3+ doping did not affect the type of crystal structure of BiOBr. In addition, the XRD peaks shifted to smaller diffraction angles, indicating that La3+ doping increased the BiOBr interplanar spacing. Meanwhile, carbon dioxide was used to characterize the photocatalytic performance of the material, and pure BiOBr, BiOBr/La-1.6%, BiOBr/La-4.9% and BiOBr/La-8.1% were generated from CH3OH showing photocatalytic efficiencies of 31.76. mu. mol g-1, 40.04. mu. mol g-1, 63.12. mu. mol-1 and 41.77. mu. mol-1, respectively, in three hours of light irradiation. The improved photocatalytic efficiency may be attributed to enhanced absorption of visible light, facilitating the separation of electron-hole pairs.

Drawings

FIG. 1: SEM image of La-doped petal-shaped BiOBr photocatalytic material.

FIG. 2: the invention discloses an XPS full spectrum of a La-doped petal-shaped BiOBr photocatalytic material.

FIG. 3: the ultraviolet-visible diffuse reflection spectrograms of all samples of the La-doped petal-shaped BiOBr photocatalytic material are shown.

FIG. 4: the invention discloses a photocurrent test chart of a La-doped petal-shaped BiOBr photocatalytic material.

FIG. 5: the carbon dioxide reduction efficiency diagrams of all samples of the La-doped petal-shaped BiOBr photocatalytic material are shown.

Detailed Description

The invention is further described below with reference to fig. 1-5, without limiting the scope of the invention.

In the following description, for purposes of clarity, not all features of an actual implementation are described, well-known functions or constructions are not described in detail since they would obscure the invention with unnecessary detail, it being understood that in the development of any actual embodiment, numerous implementation details must be set forth in order to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, changing from one implementation to another, and it being recognized that such development effort might be complex and time consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art.

Example 1

Preparation of BiOBr:

(1) 1.0933g of cetyltrimethylammonium bromide (CTAB) was weighed out into a beaker containing 16ml of Ethylene Glycol (EG) solvent and stirred for 30 minutes by a magnetic stirrer to form a white emulsion as solution A.

(2) 1.4552g of bismuth nitrate pentahydrate were weighed out and dissolved in a beaker containing 12ml of deionized water, and stirred for 30 minutes to form a colorless transparent solution as solution B.

(3) And slowly pouring the solution B into the solution A, and carrying out ultrasonic treatment for 10 minutes to achieve uniform mixing at a molecular level. The mixture was poured into a 50ml reaction vessel and heated in an oven at 160 ℃ for 12 hours.

(4) After the reaction, the mixture was centrifuged, washed three times with deionized water and absolute ethanol, and dried in a vacuum oven at 80 ℃ overnight. The resulting powder was ground for use.

Example 2

Preparation of BiOBr/La:

(1) the same procedure as in step (1) of example 1 was repeated.

(2) 0.016g of lanthanum nitrate hydrate and 1.4552g of bismuth nitrate pentahydrate are weighed together and added to 12ml of deionized water, and stirred for 30 minutes to obtain solution B.

(3) The solution B was poured into the solution A obtained in step (1) of example 1, sonicated for 10 minutes, transferred to a 50ml reaction vessel, and reacted at 160 ℃ for 12 hours.

(4) And centrifuging, washing with deionized water and absolute ethyl alcohol for three times respectively, and drying to obtain a sample named BiOBr/La-1.6%.

Example 3

Preparation of BiOBr/La:

(1) the same procedure as in step (1) of example 1 was repeated.

(2) 0.048g of lanthanum nitrate hydrate and 1.4552g of bismuth nitrate pentahydrate were weighed together into 12ml of deionized water, and stirred for 30 minutes to obtain solution B.

(4) And centrifuging, washing with deionized water and absolute ethyl alcohol for three times respectively, and drying to obtain a sample named BiOBr/La-4.9%.

Example 4

Preparation of BiOBr/La:

(1) the same procedure as in step (1) of example 1 was repeated.

(2) 0.0795g of lanthanum nitrate hydrate and 1.4552g of bismuth nitrate pentahydrate were weighed into 12ml of deionized water and stirred for 30 minutes to obtain solution B.

(4) Centrifuging, washing with deionized water and absolute ethyl alcohol for three times respectively, and drying to obtain a sample named BiOBr/La-8.1%.

100mg of the product prepared in examples 1-4 was weighed and the photocatalytic performance of BiOBr and BiOBr/La was tested by reducing carbon dioxide to methanol under visible light, as shown in FIG. 4. It was found that pure BiOBr, BiOBr/La-1.6%, BiOBr/La-4.9% and BiOBr/La-8.1% showed generation of CH3OH having photocatalytic efficiencies of 31.76. mu. molg-1, 40.04. mu. molg-1, 63.12. mu. molg-1 and 41.77. mu. molg-1, respectively, in three hours of light irradiation. It is clear that BiOBr/La-4.9% shows the best carbon dioxide conversion efficiency, which is twice that of pure BiOBr.

In conclusion, La3+ is successfully doped on the BiOBr nano-chip by a simple hydrothermal synthesis method, and the photocatalysis performance of the BiOBr is improved by the characteristics of rich electron energy level of rare earth ions and capability of being used as an electron capture center. Due to the introduction of La3+, the absorption capacity of visible light is improved, the absorption range of visible light is widened, and the transfer rate of electrons is improved, so that the performance of reducing CO2 under the visible light of BiOBr is improved.

Although the invention has been described and illustrated in some detail, it should be understood that various modifications may be made to the described embodiments or equivalents may be substituted, as will be apparent to those skilled in the art, without departing from the spirit of the invention.

Claims

1. A preparation method of a La-doped petal-shaped BiOBr photocatalytic material is characterized by comprising the following steps: the method comprises the following steps:

(1) dispersing Cetyl Trimethyl Ammonium Bromide (CTAB) in a beaker filled with Ethylene Glycol (EG) solvent, and stirring for 30 minutes by a magnetic stirrer to form white emulsion as solution A;

(2) mixing the hydrated lanthanum nitrate solution and the pentahydrated bismuth nitrate solution, and stirring for 30 minutes to obtain a solution B; pouring the solution B into the solution A, and carrying out ultrasonic treatment for 10 minutes;

(3) transferring the suspension obtained in the step (2) into a reaction kettle, and reacting for 12 hours at 160 ℃;

(4) and (4) after the reaction in the step (3) is finished, separating out a precipitate, washing and drying the precipitate to obtain the La-doped petal-shaped BiOBr photocatalytic material.

2. The method according to claim 1, wherein in step (1), the mass of cetyltrimethylammonium bromide is 1.0933 g.

3. The method as claimed in claim 1, wherein in the step (2), the mass of the hydrated lanthanum nitrate is 0g, 0.016g, 0.048g and 0.0795g respectively, and the mass of the pentahydrated bismuth nitrate is 1.4552 g.

4. The method of claim 1, wherein in step (3), the inner liner of the reaction vessel is polytetrafluoroethylene.

5. The method according to claim 1, wherein in the step (4), the molar ratio of the La element to the Bi element is theoretically 0, 1.6%, 4.9%, 8.1%.

6. La-doped petal-shaped BiOBr photocatalytic material obtained by the method according to any one of claims 1 to 4.

7. The use of the La-doped petal-shaped BiOBr photocatalytic material according to claim 5.

8. Use according to claim 6, characterized in that CO2 is used as a degradation object to test the photocatalytic performance of the prepared material and thus to find the optimal doping ratio for La doped BiOBr.

9. Use according to claim 7, wherein BiOBr/La-4.9% exhibits an optimum carbon dioxide conversion efficiency which is twice that of pure BiOBr.