阅读说明：本技术 一种Bi/BiVO4复合异质结光催化材料的制备方法 (Bi/BiVO4Preparation method of composite heterojunction photocatalytic material ) 是由 韩培林 靳一龙 刘春辉 孙学明 李苳磊 于 2021-09-26 设计创作，主要内容包括：本发明提供了一种Bi/BiVO-(4)复合异质结光催化材料的制备方法,包括以下步骤：将BiVO4与有机还原剂混合后预热并抽真空,之后在惰性气体保护下加热至反应温度进行原位还原反应。本发明所述的制备方法以BiVO-(4)为原料,在有机还原剂中通过溶剂热法原位还原合成制备出Bi/BiVO-(4)复合异质结光催化材料,该方法步骤简单,操作方便,得到了结晶良好、颗粒均匀的Bi/BiVO-(4)复合异质结光催化材料,Bi与BiVO-(4)的复合比例可以通过在反应温度下的反应时间调整,可控性高。(The invention provides a Bi/BiVO 4 The preparation method of the composite heterojunction photocatalytic material comprises the following steps: mixing BiVO4 with an organic reducing agent, preheating and vacuumizing, and then heating to the reaction temperature under the protection of inert gas to carry out in-situ reduction reaction. The preparation method of the invention uses BiVO 4 Is used as a raw material and is prepared into Bi/BiVO by in-situ reduction synthesis in an organic reducing agent through a solvothermal method 4 A composite heterojunction photocatalytic material is prepared by mixing a plurality of materials,the method has simple steps and convenient operation, and the Bi/BiVO with good crystallization and uniform particles is obtained 4 Composite heterojunction photocatalytic material, Bi and BiVO 4 The compounding ratio of (A) can be adjusted by the reaction time at the reaction temperature, and the controllability is high.)

1. Bi/BiVO₄The preparation method of the composite heterojunction photocatalytic material is characterized by comprising the following steps of:

BiVO (bismuth oxide) is added₄Mixing with an organic reducing agent, preheating and vacuumizing, and then heating to the reaction temperature under the protection of inert gas to carry out in-situ reduction reaction; preferably, Bi and BiVO₄The compounding ratio of (a) is controlled by the reaction time at the reaction temperature.

2. The method of claim 1, wherein: the organic reducing agent is oleylamine.

3. The method of claim 1, wherein: the preheating temperature is 150 ℃, the vacuumizing time is more than 30min, and the reaction temperature is 250-290 ℃.

4. The method of claim 1, wherein: the inert gas is nitrogen.

5. The method of claim 1, wherein: BiVO₄The dosage ratio of the organic reducing agent to the organic reducing agent is 1 g: 100 ml.

6. The method of claim 1, wherein the BiVO is produced by₄The preparation method comprises the following steps:

(1) uniformly mixing bismuth nitrate pentahydrate, polyvinylpyrrolidone and ethylene glycol to obtain a solution A;

(2) uniformly mixing sodium metavanadate and deionized water to obtain a solution B;

(3) dropwise adding the solution B into the solution A, and uniformly mixing to obtain a mixed solution;

(4) putting the mixed solution into a reaction kettle, and carrying out hydrothermal reaction for 10 hours at the temperature of 180 ℃.

7. The method of claim 1, further comprising the steps of:

cleaning and drying the reaction product to obtain the required Bi/BiVO₄A composite heterojunction photocatalytic material.

8. The method of claim 7, wherein: the cleaning method is to alternately wash the mixture by using toluene and absolute ethyl alcohol three times.

9. The method of claim 7, wherein: the drying temperature is 60 ℃, and the drying time is 12 h.

10. Use of the preparation process according to any one of claims 1 to 9 in the field of photocatalytic degradation.

Technical Field

The invention belongs to the field of composite material preparation, and particularly relates to Bi/BiVO₄A preparation method of a composite heterojunction photocatalytic material.

Background

The sustainable development of the human society, industrial and economy is restricted by environmental pollution, energy crisis and greenhouse effect. Solar energy is used as clean renewable energy, and has important significance on improving the environmental quality and relieving the energy shortage. The semiconductor photocatalysis technology is one of effective methods for utilizing solar energy, and is based on that under the condition of light irradiation of a photocatalyst, electrons on a valence band of a semiconductor are excited to jump to a conduction band to form photoproduction electrons and holes with strong oxidation and reduction capabilities, so that strong oxidation-reduction potential is generated, and the cracking of water molecules or the degradation of pollutants is caused. The energy-saving and environment-friendly energy-saving device has the advantages of low energy consumption, high efficiency, environmental friendliness and the like and is valued by energy and environment workers.

Bismuth-based semiconductors are a novel photocatalytic material, and are widely concerned with the excellent characteristics of good visible light absorption capacity, high photocatalytic activity, no toxicity, low price and the like, and have a very wide development space in the aspects of development of new energy and purification of environment as a novel photocatalytic material with a great development prospect. Wherein the monoclinic BiVO₄The photocatalyst is favored by the narrow forbidden band width and the higher photocatalytic activity under visible light, but the photocatalytic performance is limited due to the high recombination rate of photo-generated electrons to holes and the slow oxygen absorption kinetics of the surface. Therefore, BiVO is improved by methods of morphology regulation, ion doping, heterojunction construction, auxiliary catalyst loading and the like₄Photocatalytic efficiency and broadens the common strategies for their application.

In addition, the photocatalysis efficiency can be effectively improved by compounding the noble metal and the semiconductor, a certain amount of noble metal loaded on the surface of the semiconductor is used as a photo-generated electron acceptor, the distribution and transmission of electrons in a system are changed, and the recombination of electron-hole pairs is inhibited, so that the photocatalysis quantum yield is improved.In addition, noble metals such as Au exhibit plasmon resonance (SPR), provide additional visible light absorption and facilitate charge separation. Thus, coupling BiVO with metals or other matched semiconductors₄The prepared composite material is also the current modified BiVO₄One of the methods commonly used for photocatalytic efficiency. Bismuth (Bi) as a typical semi-metallic material has the unique characteristics of small band gap energy, low effective mass, large mean free path, large carrier movement and the like. Meanwhile, compared with noble metals, the semimetal Bi has SPR effect and can react with BiVO₄The method becomes a perfect SPR nano structure alternative in the compounding process and avoids the influence caused by foreign elements. In addition, Bi has been widely studied as a photocatalytic material capable of effectively degrading various liquid and gas phase contaminants including potassium dichromate, rhodamine B, methyl blue, congo red, and parachlorophenol. If Bi and BiVO can be converted₄The composite is an economic and practical effective way for replacing the precious metal composite.

At present, the research work at home and abroad mainly focuses on optimizing Bi/BiVO₄The composite material has synergistic effect on the visible light capturing capacity and photocatalytic activity stability. Li-writing et al synthesized Bi/BiVO by solvothermal method using sodium orthovanadate as vanadium source and bismuth chloride and bismuth nitrate hydrate as bismuth source₄Obtaining that the separation capability of the electron-hole is enhanced after the self-doping of Bi; BiVO prepared by silver and the like by sol-gel method₄Hydrothermal preparation of Bi/BiVO with commercial Bi powder₄The material with the heterostructure has a high degradation effect on rhodamine B. However, the preparation of the Bi/BiVO is that under the condition of water phase, the materials are aggregated and not dispersed to obtain Bi/BiVO₄The particle size is not uniform, thereby affecting the photocatalytic effect.

Disclosure of Invention

In view of the above, the present invention is directed to a Bi/BiVO₄Preparation method of composite heterojunction photocatalytic material to realize Bi in BiVO₄Surface in-situ reduction to obtain Bi/BiVO₄A heterojunction composite system.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

Bi/BiVO₄The preparation method of the composite heterojunction photocatalytic material comprises the following steps:

BiVO (bismuth oxide) is added₄Mixing with organic reducing agent, preheating and vacuumizing, heating to reaction temperature under the protection of inert gas to carry out in-situ reduction reaction, wherein Bi is BiVO₄Bi and BiVO obtained by surface in-situ reduction₄The compounding ratio of (a) is controlled by the reaction time at the reaction temperature.

Preferably, the organic reducing agent is oleylamine.

Preferably, the preheating temperature is 150 ℃, the vacuumizing time is more than 30min, and the reaction temperature is 250-290 ℃.

Preferably, the inert gas is nitrogen.

Preferably, BiVO₄The dosage ratio of the organic reducing agent to the organic reducing agent is 1 g: 100 ml.

Preferably, the BiVO₄The preparation method comprises the following steps:

(1) uniformly mixing bismuth nitrate pentahydrate, polyvinylpyrrolidone and ethylene glycol to obtain a solution A;

(2) uniformly mixing sodium metavanadate and deionized water to obtain a solution B;

(3) dropwise adding the solution B into the solution A, and uniformly mixing to obtain a mixed solution;

(4) putting the mixed solution into a reaction kettle, and carrying out hydrothermal reaction for 10 hours at the temperature of 180 ℃.

Preferably, the method further comprises the following steps:

cleaning and drying the reaction product to obtain the required Bi/BiVO₄A composite heterojunction photocatalytic material.

Preferably, the washing method is three times of alternate washing with toluene and absolute ethanol.

Preferably, the drying temperature is 60 ℃ and the drying time is 12 h.

The preparation method is applied to the field of photocatalytic degradation.

Compared with the prior art, the Bi/BiVO provided by the invention₄The preparation method of the composite heterojunction photocatalytic material has the following advantages:

(1) the preparation method of the invention uses BiVO₄Is used as a raw material and is prepared into Bi/BiVO by in-situ reduction synthesis in an organic reducing agent through a solvothermal method₄The method has simple steps and convenient operation, and the Bi/BiVO with good crystallization and uniform particles is obtained₄Composite heterojunction photocatalytic material, Bi and BiVO₄The compounding proportion of (A) can be adjusted by the reaction time at the reaction temperature, and the controllability is high;

(2) the preparation method takes oleylamine as an organic reducing agent and a ligand and takes BiVO₄Bi on the surface³⁺Bi nano particles are generated by in-situ reduction, so that other impurities are prevented from being introduced;

(3) BiVO used in preparation method of the invention₄The raw materials are synthesized by a hydrothermal method, the shape of the raw materials is an olive-shaped structure with surface wrinkles and fine pores, a template can be provided for the growth of Bi nanoparticles, a composite system with good crystallization and uniform particles is prepared, the electron flow and distribution in the system are changed, the raw materials and the composite system are in better contact when pollutants are degraded, and the photocatalytic performance of the material is improved;

(4) the raw materials adopted by the preparation method are all non-toxic, green and environment-friendly, and belong to environment-friendly reactions.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 shows BiVO according to an embodiment of the present invention₄Scanning electron microscope photographs of (a);

FIG. 2 shows Bi/BiVO prepared in examples 1, 2 and 3 of the present invention₄An X-ray diffraction pattern of a composite heterojunction photocatalytic material, wherein a is example 1, b is example 2, and c is example 3;

FIG. 3 shows Bi/BiVO prepared in examples 3, 4, 5 and 6 of the present invention₄X-ray diffraction pattern of a composite heterojunction photocatalytic material, wherein a is example 3, b is example 4, and c isExample 5, d is example 6;

FIG. 4 shows Bi/BiVO prepared in example 3₄Scanning electron micrographs of the composite heterojunction photocatalytic material;

FIG. 5 shows Bi/BiVO prepared in example 4₄Scanning electron micrographs of the composite heterojunction photocatalytic material;

FIG. 6 shows Bi/BiVO prepared in example 5₄Scanning electron micrographs of the composite heterojunction photocatalytic material;

FIG. 7 shows Bi/BiVO prepared in example 6₄Scanning electron micrographs of the composite heterojunction photocatalytic material;

FIG. 8 shows BiVO according to an embodiment of the present invention₄Bi/BiVO prepared in examples 3, 4, 5 and 6₄And (3) a degradation rate diagram of the composite heterojunction photocatalytic material photodegradation rhodamine B solution.

Detailed Description

Unless defined otherwise, technical terms used in the following examples have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods are conventional methods unless otherwise specified.

The present invention will be described in detail with reference to the following examples and accompanying drawings.

Example 1

1. Hydrothermal method for preparing BiVO₄

1.1 washing a polytetrafluoroethylene reaction kettle with the volume of 50mL by tap water, distilled water and absolute ethyl alcohol respectively for 1-3 times in sequence, and drying for later use;

1.2 weighing 0.1617g Bi (NO) with an electronic balance₃)₃·5H₂Adding 25mL of ethylene glycol into a clean beaker with the volume of 50mL of O and 1g of polyvinylpyrrolidone, stirring and mixing uniformly, and marking as a solution A; weighing 0.06g NaVO₃In a clean beaker with a volume of 50mL, 15mL of deionized water was added, and the mixture was labeled as solution B after stirring and mixing well. Solution B was then added dropwise to solution a with vigorous stirring of solution a. After stirring and mixing uniformly, the mixture obtained is transferred toPlacing the reaction kettle with the volume of 50mL of polytetrafluoroethylene in a temperature of 180 ℃ for hydrothermal reaction for 10 h. Cooling to room temperature after the reaction is finished, alternately washing the reaction product for 3 times by using absolute ethyl alcohol and deionized water, and drying for 4 hours at 80 ℃ to obtain BiVO₄. The product was a bright yellow powder particle. The microstructure under the scanning electron microscope is a rugby-shaped structure with regular shape and uniform size, as shown in fig. 1.

2. Preparation of Bi/BiVO₄Composite heterojunction photocatalytic material

2.1 washing a two-neck flask with the volume of 50mL with tap water, distilled water and absolute ethyl alcohol respectively for 2 times in sequence, and drying for later use;

2.2 to a clean two-necked flask with a volume of 50mL was added 0.1g of BiVO prepared by hydrothermal method₄Then 10mL of oleylamine is added, stirred and mixed evenly, the mixture is vacuumized for 30min when the temperature is raised to 150 ℃ under magnetic stirring to remove internal oxygen and moisture, and then the mixture is heated to 250 ℃ under the protection of nitrogen and reacts for 30min at the temperature. After the reaction is finished, alternately washing the product with toluene and absolute ethyl alcohol for three times, and drying at 60 ℃ for 12h to obtain Bi/BiVO after in-situ reduction for 30min₄A composite heterojunction photocatalytic material. The product is dark green powder particles, and the crystal structure of the product is represented by an X-ray powder diffractometer, as shown by a curve in figure 2.

Example 2

The difference from example 1 is that in step 2.2, the temperature is increased to 270 ℃ under the protection of nitrogen, and the reaction is carried out for 30min at the temperature. The other operation steps are the same as in example 1. Obtaining Bi/BiVO when in-situ reduction is carried out for 30min₄A composite heterojunction photocatalytic material. The product is dark green powder particles, and the crystal structure of the product is represented by an X-ray powder diffractometer, as shown by a curve b in figure 2.

Example 3

The difference from example 1 is that in step 2.2, the temperature is raised to 290 ℃ under the protection of nitrogen, and the reaction is carried out for 30min at the temperature. The other operation steps are the same as in example 1. Obtaining Bi/BiVO when in-situ reduction is carried out for 30min₄A composite heterojunction photocatalytic material. The product is dark green powder granule, and its crystal structure is characterized by X-ray powder diffractometer, such as curve c in FIG. 2 and curve c in FIG. 3The microstructure under the scanning electron microscope is a loose structure with a uniform distribution of size particles, as shown in the a curve, as shown in fig. 4.

Example 4

The difference from example 3 is that in step 2.2, the temperature is raised to 290 ℃ under the protection of nitrogen, and the reaction is carried out for 1h at the temperature. The other operation steps are the same as in example 1. Obtaining Bi/BiVO when in-situ reduction is carried out for 1h₄A composite heterojunction photocatalytic material. The product is black powder particles, the crystal structure of the product is represented by an X-ray powder diffractometer, as shown by a curve b in figure 3, and the microstructure under a scanning electron microscope is a loose structure with uniformly distributed particles, as shown in figure 5.

Example 5

The difference from example 3 is that in step 2.2, the temperature is raised to 290 ℃ under the protection of nitrogen, and the reaction is carried out for 2h at the temperature. The other operation steps are the same as in example 1. Obtaining Bi/BiVO when in-situ reduction is carried out for 2h₄A composite heterojunction photocatalytic material. The product is black powder particles, the crystal structure of the product is represented by an X-ray powder diffractometer, as shown by a curve c in figure 3, and the microstructure under a scanning electron microscope is a loose structure with uniformly distributed particles, as shown in figure 6.

Example 6

The difference from example 3 is that in step 2.2, the temperature is raised to 290 ℃ under the protection of nitrogen, and the reaction is carried out for 3h at the temperature. The other operation steps are the same as in example 1. Obtaining Bi/BiVO when in-situ reduction is carried out for 3 hours₄A composite heterojunction photocatalytic material. The product is black powder particles, the crystal structure of the product is represented by an X-ray powder diffractometer, as shown by a curve d in figure 3, and the microstructure under a scanning electron microscope is a loose structure with uniformly distributed particles, as shown in figure 7.

As shown in FIGS. 2 and 3, BiVO was observed from the bottom vertical line of all peaks except for the Bi diffraction peak labeled diamond-solid₄The standard diffraction peak of (a) corresponds to the standard diffraction peak of (b), and no other impurity peak appears.

Verification of photocatalytic effect

1. Preparation of 10 mg. L^-1Rhodamine B solution; a glass test tube having a volume of 50mL and a volume of 4 were placed.Washing 5mL of quartz cuvette with distilled water and absolute ethyl alcohol respectively for 2 times, and drying for later use;

2. 10mg of Bi/BiVO prepared in examples 3, 4, 5 and 6 were added to 5 50 mL-volume clean glass tubes₄Composite and BiVO prepared in example 1₄Then respectively adding 30mL of rhodamine B solution (10 mg. L)^-1) After being dispersed uniformly by ultrasonic waves, the solution is placed into a photocatalytic reactor, the sample and the solution are stirred for 1 hour under the condition of keeping out of the sun to enable the sample and the solution to reach adsorption-desorption balance, then a photocatalytic degradation experiment is carried out under the irradiation of a 300W ultraviolet lamp, a certain amount of solution is taken every 30 minutes for centrifugal separation, the supernatant is taken to measure the change of the absorbance, the degradation rate is shown in figure 8, the degradation time is 2.5 hours, and the Bi/BiVO prepared in examples 3, 4, 5 and 6 has the advantages of high stability, high stability and the like₄Composite and BiVO prepared in example 1₄The degradation rates of (a) were 53%, 78%, 45%, 27% and 34%, respectively.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.