CN107376950B - Nano composite photocatalytic film material and preparation method thereof - Google Patents

Abstract

The invention belongs to the field of photocatalysis, and particularly relates to a photocatalytic film material and a preparation method thereof. The BiOI and the BiOBr with the molar ratio of 0.1-0.5 are formed into the BiOI/BiOBr nano composite photocatalytic film material with a sheet-shaped layered structure by an in-situ growth method and an ion exchange mode. The preparation process adopts in-situ growth combined with an ion exchange method to prepare the BiOI/BiOBr material which can be well attached to the surface of a stainless steel matrix to form a layer of film material with visible light catalytic activity. The preparation method provided by the invention is simple in process, easy to control and low in cost, constructs the BiOI/BiOBr nano composite sheet film structure with the visible light catalytic effect, and has potential application prospects in the fields of water body purification, marine antifouling and the like.

Description

A kind of nanocomposite photocatalytic film material and preparation method thereof

technical field

The invention belongs to the field of photocatalysis, in particular to a photocatalytic film material and a preparation method thereof.

Background technique

With the overall progress of human society, human beings have an increasing impact on the original natural ecology, and a series of environmental problems have been caused by the excessive exploitation and utilization of natural resources. Among them, environmental problems such as water scarcity and water pollution are becoming increasingly prominent. Therefore, sewage treatment is particularly important. Among many sewage treatment processes, photocatalytic oxidation degradation technology has outstanding advantages such as high efficiency, non-selectivity, high stability, green non-toxicity, no secondary pollution, low energy consumption, simple operation and low cost. Especially in recent years, semiconductor photocatalytic materials represented by nano-TiO ₂ have been found to be a good photocatalyst for water treatment. They can generate electron-hole pairs under illumination conditions, and part of the electrons and holes can migrate to the semiconductor. The surface reacts with O ₂ , OH ^- etc. in the water environment to generate radicals with strong chemical oxidation activity. These free radicals, photogenerated electrons and holes can directly interact with the reactants to be degraded and oxidatively decompose them to achieve the effect of photocatalytic degradation of organic pollutants.

BiOX(X=Cl, Br, I) bismuth series compounds have high electron-hole pair separation efficiency due to the strong built-in electric field between [Bi ₂ O ₂ ] ²⁺ and the halogen layer. , showing high visible light photocatalytic activity. However, due to the inherent energy band structure, BiOX monomer materials often have limited ability to catalyze the degradation of organic pollutants under visible light, which greatly limits the application of such photocatalytic materials in the field of water treatment.

In recent years, nano-inorganic composite materials have been greatly developed. Nano-scale composites can endow materials with more comprehensive properties, solve the application limitations of single-structure inorganic functional materials, and improve material properties and application scope. For example, the heterojunction structure formed by the effective recombination of two inorganic semiconductor nanomaterials can improve the photo-generated electron-hole separation efficiency and greatly improve the photocatalytic efficiency of the material. If the existing photocatalytic materials are modified by nanocomposite technology to improve the material properties, the application of such materials in the field of water treatment will be greatly expanded. However, although various composite materials with different morphologies have been synthesized successively under different methods, such as the commonly used hydrothermal method, solvothermal method, and sonochemical method. Considering that the composite materials prepared by these methods are all nano-materials in powder form, and in specific industrial application environments, nano-powder materials generally have difficulties in recycling, poor recycling rate, and greatly increase the cost of water treatment. Therefore, the effective immobilization of photocatalysts, especially nanocomposite photocatalysts, is an unavoidable problem in the practical application and promotion of photocatalytic water treatment industry.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, the purpose of the present invention is to provide a nanocomposite photocatalytic film material and a preparation method thereof.

To achieve the above object, the present invention adopts the following technical solutions to implement:

A nano-composite photocatalyst thin film material, the BiOI/BiOBr nano-composite photocatalytic thin film material with a lamellar structure is formed by the in-situ growth method and the ion exchange method to form BiOI and BiOBr with a molar ratio of 0.1-0.5.

Preparation method of nanocomposite photocatalyst film material:

1) Disperse Bi(NO ₃ ) ₃ .5H ₂ O in excess ethylene glycol and add PVP surfactant, then add KI aqueous solution in an equimolar amount with Bi(NO ₃ ) ₃ .5H ₂ O, wait for two After mixing evenly, transfer to the inner lining of the reaction kettle, then immerse the pretreated substrate to be protected in the above mixture, react at 120-160°C for 4-12 hours, take out for washing, dry, and wait for use;

2) Dissolve tetrabutylammonium bromide in excess water, transfer to the inner lining of the reactor after dissolving, then immerse the above-mentioned dried back matrix in the mixed solution in the reactor, at 120～160 ℃, react 12～ 36h, that is, a BiOI/BiOBr nanocomposite photocatalytic film with a lamellar structure was formed on the surface of the substrate.

The total concentration range of PVP in step 1) is 0.05-2 g/L.

The concentration of the reactants Bi(NO ₃ ) ₃ ·5H ₂ O and KI used in step 1) is 0.05-0.15 mol/L.

In step 2), the concentration of tetrabutylammonium bromide is 1-12 mmol/L.

Application of the thin film material as a photocatalyst.

Application of the film material in sewage treatment or anti-biofouling.

The beneficial effects of the present invention are:

The invention adopts the in-situ growth method and the ion exchange method to prepare the BiOI/BiOBr nano-composite photocatalytic thin film material with lamellar structure on the surface of the iron substrate. It solves the problem of immobilization of nanocomposite photocatalytic materials very well. Compared with the nanocomposite photocatalytic film material prepared by the commonly used sol-gel method, it has the technical advantages of one-time molding and simple operation. This specific structure of BiOI/BiOBr nanocomposite photocatalytic curing film material has high photocatalytic performance, the degradation rate of rhodamine B can reach 91% under visible light for 60 minutes, and the killing rate of Escherichia coli for 2 hours under visible light is over 99.9%. ;specific:

(1) The preparation method adopted in the present invention has simple process, easy control and low cost.

(2) The prepared BiOI/BiOBr nanocomposite photocatalytic film material with lamellar structure has broad application prospects in sewage treatment and anti-biofouling.

Description of drawings

Fig. 1 is the X-ray diffraction (XRD) pattern of BiOI/BiOBr thin film prepared by the present invention (wherein the abscissa is 2θ (angle), the unit is degree (degree); the ordinate is Intensity (intensity), the unit is a.u. (absolute unit)).

FIG. 2 is a scanning electron microscope (SEM) photograph of the BiOI/BiOBr thin film prepared by the present invention.

FIG. 3 is the ultraviolet-visible diffuse reflection absorption (UV-DRS) spectrum of the BiOI/BiOBr thin film prepared by the present invention.

Detailed ways

The present invention will be further described below through specific examples, which will help those skilled in the art to understand the present invention more comprehensively, but will not limit the present invention in any way.

In the invention, the BiOI/BiOBr nanocomposite photocatalytic thin film material with lamellar structure is prepared on the surface of the stainless steel substrate by in-situ growth combined with the ion exchange method. Since the BiOI/BiOBr nanocomposite is directly prepared in situ on the surface of the stainless steel substrate, the BiOI/BiOBr nanocomposite thin film material has a strong bonding force with the surface of the stainless steel substrate, which ensures the structural stability of the thin film. The photocatalytic thin film material has good visible light absorption performance, and its sheet-like structure accelerates the separation of photogenerated carriers, reduces the recombination probability of photogenerated electron-hole pairs, and exhibits an efficient photocatalytic effect under visible light. It has good practical value and potential application prospects in the fields of water purification and marine antifouling. Meanwhile, the nanocomposite photocatalyst thin film material also has the characteristics of uniform film formation, low price and good repeatability.

Example 1: Preparation method of BiOI/BiOBr nanocomposite photocatalytic thin film material with lamellar structure

Firstly, the BiOI precursor thin film material with lamellar structure was prepared on the surface of stainless steel substrate by in-situ growth under hydrothermal conditions. Weigh 8 mmol Bi(NO ₃ ) ₃ ·5H ₂ O and 0.1 g PVP into 70 mL of ethylene glycol, disperse by ultrasonic for 30 min, weigh 8 mmol KI and dissolve it in 10 mL of water, then mix the two solutions uniformly, and transfer to 100 mL in the reactor. Immerse the pre-treated stainless steel mesh in the above mixed solution. Then the reaction kettle was heated to 140°C, and the reaction time was 4h. After the reaction was completed, the stainless steel mesh was taken out, rinsed with absolute ethanol and distilled water in turn, and finally placed in a drying oven at 60°C for drying for 6 hours. Weigh 0.48 mmol of tetrabutylammonium bromide and add it to 80 mL of water, dissolve it with magnetic stirring, and transfer it to a 100 mL reaction kettle. The aforementioned stainless steel mesh was immersed in the aforementioned mixed solution again. Then the reaction kettle was heated to 140°C, and the reaction time was 24h. After the reaction was completed, the stainless steel mesh was taken out, rinsed with absolute ethanol and distilled water in turn, and finally placed in a drying oven at 60°C for drying for 6 hours.

Characterization of BiOI/BiOBr nanocomposite photocatalytic thin film materials:

The results of X-ray diffraction analysis in Figure 1 show that the composite material only contains BiOI and BiOBr; the X-ray energy spectrum analysis results show that the molar ratio of BiOI/BiOBr in the nanocomposite photocatalytic material is 0.27; from the scanning electron microscope of Figure 2 The photo shows that BiOI and BiOBr materials are in sheet shape, and a larger part of the sheet material is perpendicular to the surface of the stainless steel mesh substrate, and the crystallinity is high. This sheet film layered structure will have a large specific surface area and good visible light absorption performance. (See UV-DRS spectrum in Figure 3).

Example 2: Preparation method of BiOI/BiOBr nanocomposite photocatalytic thin film material with lamellar structure

Firstly, the BiOI precursor thin film material with lamellar structure was prepared on the surface of stainless steel substrate by in-situ growth under hydrothermal conditions. Weigh 4mmol Bi(NO ₃ ) ₃ ·5H ₂ O and 0.2g PVP into 70mL ethylene glycol, disperse by ultrasonic for 30min, weigh 4mmol KI and dissolve in 10mL water, then mix the two solutions uniformly, and transfer to 100mL in the reactor. Immerse the pre-treated stainless steel mesh in the above mixed solution. Then the reaction kettle was heated to 160°C, and the reaction time was 8h. After the reaction was completed, the stainless steel mesh was taken out, rinsed with absolute ethanol and distilled water in turn, and finally placed in a drying oven at 60°C for drying for 6 hours. 0.80 mmol of tetrabutylammonium bromide was weighed and added to 80 mL of water, dissolved by magnetic stirring, and then transferred to a 100 mL reaction kettle. The aforementioned stainless steel mesh was immersed in the aforementioned mixed solution again. Then the reaction kettle was heated to 160°C, and the reaction time was 36h. After the reaction was completed, the stainless steel mesh was taken out, rinsed with absolute ethanol and distilled water in turn, and finally placed in a drying oven at 60°C for drying for 6 hours.

Example 3: Preparation method of BiOI/BiOBr nanocomposite photocatalytic thin film material with lamellar structure

Firstly, the BiOI precursor thin film material with lamellar structure was prepared on the surface of stainless steel substrate by in-situ growth under hydrothermal conditions. Weigh 12mmol Bi(NO ₃ ) ₃ ·5H ₂ O and 0.05g PVP into 70mL ethylene glycol, ultrasonically disperse for 30min, weigh 12mmol KI and dissolve in 10mL water, then mix the two solutions uniformly, and transfer to 100mL in the reactor. Immerse the pre-treated stainless steel mesh in the above mixed solution. Then the reaction kettle was heated to 120°C, and the reaction time was 12h. After the reaction was completed, the stainless steel mesh was taken out, rinsed with absolute ethanol and distilled water in turn, and finally placed in a drying oven at 60°C for drying for 6 hours. 0.16 mmol of tetrabutylammonium bromide was weighed and added to 80 mL of water, dissolved by magnetic stirring, and then transferred to a 100 mL reaction kettle. The aforementioned stainless steel mesh was immersed in the aforementioned mixed solution again. Then the reaction kettle was heated to 120°C, and the reaction time was 12h. After the reaction was completed, the stainless steel mesh was taken out, rinsed with absolute ethanol and distilled water in turn, and finally placed in a drying oven at 60°C for drying for 6 hours.

Example 4

计算其此次光催化降解率η。可见光照60min对罗丹明B的降解率可达到91％。The BiOI/BiOBr nanocomposite photocatalytic thin film material of a certain area (generally 15×40 mm ² ) prepared in the above-mentioned embodiment to obtain a flaky layered structure is spread and placed in a quartz test tube, followed by adding a certain amount of Rhodin with an appropriate concentration. Bright B, placed in a photoreactor for photocatalytic reaction for a certain period of time. Aspirate the organic matter in the quartz tube, and measure its concentration C _t , and press

Calculate the photocatalytic degradation rate η this time. The degradation rate of rhodamine B under visible light for 60 min can reach 91%.

A certain area (generally 15×40 mm ² ) of BiOI/BiOBr nanocomposite photocatalytic thin film material with a lamellar structure prepared in the above-mentioned example was spread in a quartz test tube after UV sterilization, and 4 mL of bacteria was added to the concentration of about PBS bacterial solution on the order of 10 ⁶ cfu/mL. Subsequent experimental procedures were the same. The reaction system was sampled under dark conditions for a certain period of time (30 min) and illuminated for a certain period of time, and the bacterial survival rate and sterilization rate were determined by plate counting method. The killing rate of Escherichia coli was more than 99.9% under visible light for 2 hours.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, some modifications and improvements can be made without departing from the inventive concept of the present invention, which belong to the present invention. the scope of protection of the invention.

Claims (7)

1. a nano-composite photocatalyst film material, is characterized in that: the BiOI/BiOBr nano-composite photocatalysis that makes mol ratio be 0.1～0.5 BiOI and BiOBr form lamellar structure with the mode of in-situ growth method and ion exchange film material; The preparation method of the nanocomposite photocatalyst film material is as follows: 1) Disperse Bi(NO ₃ ) ₃ ·5H ₂ O in excess ethylene glycol, add PVP surfactant, and then add Bi(NO ₃ ) ₃ · The KI aqueous solution of equimolar amount of 5H ₂ O is transferred to the inner lining of the reactor after the two are evenly mixed, and then the pretreated substrate to be protected is immersed in the above mixed solution, and at 120 ~ 160 ° C, the reaction is performed for 4 ~ 12 h, take out, wash, dry, and set aside; 2) Dissolve tetrabutylammonium bromide in excess water, transfer to the inner lining of the reactor after dissolving, then immerse the above-mentioned dried matrix in the mixed solution in the reactor, at 120 ~ 160 ° C, react for 12 ~36 h, that is, the BiOI/BiOBr nanocomposite photocatalytic film with lamellar structure was formed on the surface of the substrate. 2. by the preparation method of the described nanocomposite photocatalyst film material of claim 1, it is characterized in that: 1) Disperse Bi(NO ₃ ) ₃ ·5H ₂ O in excess ethylene glycol and add PVP surfactant, then add KI aqueous solution in an equimolar amount with Bi(NO ₃ ) ₃ ·5H ₂ O, wait for two After mixing evenly, transfer to the lining of the reactor, then immerse the pretreated substrate to be protected in the above mixture, react at 120~160 °C for 4~12 h, take out for washing, dry, and set aside for use; 2) Dissolve tetrabutylammonium bromide in excess water, transfer to the inner lining of the reactor after dissolving, then immerse the above-mentioned dried matrix in the mixed solution in the reactor, at 120 ~ 160 ° C, react for 12 ~36 h, that is, the BiOI/BiOBr nanocomposite photocatalytic film with lamellar structure was formed on the surface of the substrate. 3 . The method for preparing a nanocomposite photocatalyst thin film material according to claim 2 , wherein the concentration range of the PVP in step 1) is 0.05-2 g/L. 4 . 4 . The preparation method of nanocomposite photocatalyst thin film material according to claim 2 , wherein the reactants Bi(NO ₃ ) ₃ .5H ₂ O and KI used in step 1) have a concentration of 0.05~ 0.15 mol/L. 5 . The method for preparing a nanocomposite photocatalyst film material according to claim 2 , wherein the concentration of tetrabutylammonium bromide in step 2) is 1-12 mmol/L. 6 . 6 . The application of the nanocomposite photocatalyst thin film material according to claim 1 , wherein the thin film material is used as a photocatalyst. 7 . 7 . The application of the nanocomposite photocatalyst thin film material according to claim 1 , wherein: the application of the thin film material in sewage treatment or anti-biological fouling. 8 .

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