CN107649118B - BiVO4Supported mixed crystalline phase TiO2Preparation method of visible light composite photocatalyst - Google Patents

Abstract

TiO₂As a common semiconductor material, the application of the material in the field of photocatalysis is severely restricted by the defects of low quantum efficiency, no response to visible light and the like. The invention uses isopropyl titanate as raw material, firstly prepares amorphous TiO₂Preparing TiO with anatase/brookite mixed crystal phase by using micron spheres through green and environment-friendly hydrothermal process₂The mesoporous sphere has a structure composed of nano particles, and reduces the recombination effect in the charge transfer process through the nanocrystallization process. Secondly, BiVO is prepared by a simple wet chemical method₄Nanoparticle loading to TiO₂On the mesoporous spheres, the obtained heterostructure has good visible light response and has a visible light degradation effect on methylene blue. BiVO₄/TiO₂The composite photocatalyst exists in the form of micron-sized spherical particles formed by self-assembly of primary nano particles, is easy to recover from sewage, and has very important practical significance in industrial wastewater treatment.

Description

BiVO4Supported mixed crystalline phase TiO2Preparation method of visible light composite photocatalyst

The technical field is as follows:

the invention relates to BiVO₄Supported TiO₂Preparation method of mesoporous microsphere structured photocatalyst, in particular to preparation of TiO containing anatase/brookite mixed crystal phase by hydrothermal method₂The flower-like nano structure is used as a carrier, and BiVO is prepared by a wet chemical method₄Nanoparticle loading to TiO₂And preparing the heterojunction nano photocatalyst with visible light response. The technology belongs to the field of nano material preparation.

Background art:

in recent years, with the rapid development of social economy, the problem of environmental pollution is increasingly highlighted. The national high standard for industrial wastewater discharge requires that enterprises, particularly small and medium-sized enterprises, find an efficient and economic sewage treatment method.

The semiconductor photocatalysis technology is an efficient technology which utilizes solar energy to carry out catalytic reaction and is established in recent decades, and is widely applied to the aspects of hydrogen production by photolysis, organic matter photocatalytic degradation and the like. In 1972, Fujishima et al used TiO₂The photoelectrode decomposes water, and the research of photocatalysis technology has been raised from the water decomposition. Titanium dioxide, as a semiconductor material, has received wide attention from society due to its low cost, non-toxic, harmless, and high chemical stability. However, titanium dioxide has some outstanding disadvantages, which limit its application in the field of photocatalysis:

(1) the quantum efficiency of titanium dioxide is low, the recombination rate of photoproduction electron-cavity is high, the transfer of photoproduction charge can be improved by nano-processing the titanium dioxide, but certain difficulty is generated in the recovery of the catalyst in industry;

(2) the forbidden band width of titanium dioxide is 3.2eV, and only ultraviolet light with the wavelength less than 387nm can be utilized, and the ultraviolet light part only accounts for about 4% of the solar spectrum, so that the utilization of the light energy is greatly limited.

To solve the above problems, TiO is generally used₂The material is modified. On one hand, through the self-assembly process, on the basis of titanium dioxide nanocrystallization, more complex nano-tubes, nano-rods and 3D nano-structures are constructed, and the structures form secondary structures with larger sizes by primary particles with nano-sizes, so that the sedimentation and recovery of the catalyst are facilitated. And on the other hand, the modification is carried out by means of ion doping, precious metal deposition, semiconductor compounding and the like, wherein the semiconductor compounding is a more effective mode. Bismuth vanadate acts as a narrow bandgap (2.4eV) semiconductor, but because of its shorter electron transport length, it generally does not perform well when used alone as a photocatalyst. Can be used in combination with TiO₂The light absorption range of the photocatalyst is enhanced through compounding, the purpose of prolonging the charge separation life is achieved through the construction of a heterojunction, and the photocatalytic efficiency is improved. About BiVO at present₄Supported TiO₂The reports of the composite photocatalyst are few, and most researches focus on preparing BiVO firstly₄Particles, and sol-gel processing of TiO₂Loaded in BiVO₄Surfaces (Applied Catalysis B: Environmental 104(2011)30-36, Journal of Alloys and Compounds 688(2016) 703-711); and the prepared BiVO₄Supported TiO₂Most of them exist in the form of dispersed small particles (Chemical Engineering Journal 314(2017) 443-. It is worth mentioning that almost no BiVO exists at present₄TiO of supported mixed crystal phase₂The related report of spherical visible light catalyst.

The invention content is as follows:

the invention aims to provide a BiVO₄Supported mixed crystalline phase TiO₂The preparation method of the visible light catalyst overcomes the defects in the prior art, the scheme can realize semiconductor compounding to improve the catalytic activity of the catalyst, and simultaneously exists in a micron mesoporous sphere form formed by self-assembling nano particles, so that the visible light catalyst is easy to separate from a liquid phase, is not easy to cause secondary pollution, and is beneficial to recycling of the catalyst.

To achieve the above object and solve the above problems, a BiVO is provided according to the following technical means₄Supported mixed crystalline phase TiO₂The preparation method of the visible light photocatalyst comprises the following steps:

(1) selecting isopropyl titanate (TTIP) as a raw material, dissolving the isopropyl titanate (TTIP) in 500mL of ethanol, and adding a certain amount of 0.1 mol.L^-1The KCl solution is used for initiating a hydrolysis reaction, the stirring is stopped after white precipitation occurs, and the mixture is kept stand for 12 to 48 hours. Centrifuging, washing and drying to obtain white TiO₂·nH₂O powder;

(2) 0.6g of the powder of (1) was added to a solution containing 60mL of 0.1 mol. L^-10.9mL of hydrogen peroxide with the mass fraction of 3 percent is dripped into the inner liner of the NaOH solution hydrothermal kettle and reacts for 2 to 20 hours in a forced air drying oven at the temperature of 140 ℃ and 200 ℃. Cooling to room temperature, centrifuging, washing and drying the product to obtain white sodium titanate powder;

(3) 1.0g of sodium titanate powder was added to 250mL of 0.1M diluentThe mixture was stirred well in hydrochloric acid for 1 hour and then allowed to stand for 1 hour. And centrifuging, washing and drying the product. Calcining the obtained white product in a muffle furnace at 400-₂Mesoporous sphere powder;

(4) 2.425g of Bi (NO)₃)₃·5H₂O was added to 100mL of 0.4 mol. L^-1Fully stirring the solution to obtain the bismuth nitrate solution. 0.585g of NH₄VO₃Adding the mixture into 100mL of 80 ℃ deionized water, fully stirring to obtain an ammonium metavanadate solution, and adding a certain mass of TiO obtained in the step (3)₂The mixture was stirred well through a porous ball, and the bismuth vanadate solution was added dropwise to the solution. The pH of the system was adjusted to 4 using ammonia and the mixture was evaporated by heating in a water bath at 90 ℃ to give a bright yellow slurry. Washing, centrifuging and drying to obtain bright yellow powder;

(5) calcining the powder obtained in the step (4) in a muffle furnace at the temperature of 400-₄Supported mixed crystalline phase TiO₂A visible light photocatalyst.

BiVO selected for use in this patent₄As an important narrow bandgap (about 2.4eV) semiconductor material, it is usually used alone as a visible light photocatalyst and can be regarded as an excellent photosensitizer. BiVO (bismuth oxide) is added₄With TiO₂Compounding can obviously widen TiO₂The corresponding range of the spectrum of (a). When the energy of the incident light is not sufficient to excite the TiO₂BiVO when generating photo-generated electron-hole to initiate redox reaction₄But can be excited, thereby improving the utilization rate of solar energy. Second, mixed crystal phase TiO₂The structure can form a heterostructure, and the separation effect of photo-generated charges is further enhanced. Finally, compared with other appearances, the composite photocatalyst exists in the form of secondary mesoporous microspheres formed by self-assembly of nano particles, and is favorable for recycling the catalyst from sewage after use.

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention prepares BiVO by a wet chemical method₄Supported TiO₂Mesoporous micron sphere junctionThe structure and the equipment are simple and convenient, and the cost is lower.

(2) BiVO using narrow band gap semiconductor₄With TiO₂Compounding, widening the spectral response range and improving the solar energy utilization rate.

(3) Flower-like TiO₂The precursor structure enables BiVO₄The contact area is increased, a good heterostructure is formed, and the recombination of photo-generated electrons and holes is enhanced and inhibited; simultaneous TiO 2₂The mixed phase of anatase/brookite further enhances the separation effect.

(4) The composite photocatalyst exists in the form of secondary mesoporous microspheres formed by self-assembly of nano particles, is easy to recycle from treated sewage, avoids secondary pollution, and is an environment-friendly photocatalyst.

Description of the drawings:

FIG. 1: mixed crystal phase TiO₂TEM picture of flower-like sphere precursor

FIG. 2: BiVO in example 1₄/TiO₂TEM picture of mesoporous microsphere

FIG. 3: BiVO in example 1₄/TiO₂Spectral response of mesoporous microspheres

The specific implementation mode is as follows:

example 1

2mL of 0.1 mol. L was added to 500mL of ethanol^-1The solution was stirred for 10 min. 9mL of TTIP was added and stirred for 30 minutes. After standing for 24 hours, the white turbid liquid is centrifuged, washed by ethanol and water and dried. 0.6g of the above product was added to 60mL of 0.1 mol. L^-1And stirring the solution for 30 minutes in NaOH solution, then adding 0.9mL of hydrogen peroxide solution with the mass fraction of 3%, stirring the solution for 2 minutes, and packaging the hydrothermal kettle to react for 10 hours in an air-blast drying oven at 180 ℃. And (4) taking out the hydrothermal kettle, cooling to room temperature, washing the product with water, and drying. 1.0g of the above product was added to 250ml of 0.1 mol. L^-1The stirring was continued for 1 hour, and then the stirring was stopped and the mixture was allowed to stand for 1 hour. Then, the supernatant was poured off, washed with water, and the product was dried and calcined in a muffle furnace at 450 ℃ for 2 hours. Weighing 2.425g Bi (NO)₃)₃Adding to 100mL of 0.4 mol. L^-1Stirring for 30min to formSolution A. 0.585g of NH are weighed₄VO₃Adding into 100mL deionized water, heating in 80 deg.C water bath, stirring, adding 3.994g TiO₂Stirring for 10min to form suspension B. The solution A was slowly added dropwise to the suspension B, and stirred for 30 min. Adjusting the pH value of the solution to 4 by ammonia water, and obtaining bright yellow slurry in a water bath at 90 ℃. Washed by water, dried and calcined in a muffle furnace for 2h at 450 ℃. So as to obtain the product with the molar ratio of Bi: BiVO with Ti 1:10₄Supported mixed crystal phase TiO₂A mesoporous composite photocatalyst. FIG. 2 is BiVO₄/TiO₂TEM picture of mesoporous microsphere, FIG. 3 is BiVO₄/TiO₂Spectrum response diagram of the mesoporous microsphere.

Example 2

2mL of 0.1 mol. L was added to 500mL of ethanol^-1The solution was stirred for 10 min. 9mL of TTIP was added and stirred for 30 minutes. After standing for 24 hours, the white turbid liquid is centrifuged, washed by ethanol and water and dried. 0.6g of the above product was added to 60mL of 0.1 mol. L^-1And stirring the solution for 30 minutes in NaOH solution, then adding 0.9mL of hydrogen peroxide solution with the mass fraction of 3%, stirring the solution for 2 minutes, and packaging the hydrothermal kettle to react for 10 hours in an air-blast drying oven at 180 ℃. And (4) taking out the hydrothermal kettle, cooling to room temperature, washing the product with water, and drying. 1.0g of the above product was added to 250ml of 0.1 mol. L^-1The stirring was continued for 1 hour, and then the stirring was stopped and the mixture was allowed to stand for 1 hour. Then, the supernatant was poured off, washed with water, and the product was dried and calcined in a muffle furnace at 450 ℃ for 2 hours. Weighing 2.425g Bi (NO)₃)₃Adding to 100mL of 0.4 mol. L^-1Is stirred for 30min to form a solution A. 0.585g of NH are weighed₄VO₃Adding into 100mL deionized water, heating in 80 deg.C water bath, stirring, adding 19.966g TiO₂Stirring for 10min to form suspension B. The solution A was slowly added dropwise to the suspension B, and stirred for 30 min. Adjusting the pH value of the solution to 4 by ammonia water, and obtaining bright yellow slurry in a water bath at 90 ℃. Washed by water, dried and calcined in a muffle furnace for 2h at 450 ℃. So as to obtain the product with the molar ratio of Bi: BiVO with Ti 1:50₄Supported mixed crystal phase TiO₂A mesoporous composite photocatalyst.

Claims (2)

1. BiVO₄Supported mixed crystalline phase TiO₂The preparation method of the visible light photocatalyst is characterized by comprising the following steps of:

(1) selecting isopropyl titanate (TTIP) as a raw material, dissolving the isopropyl titanate (TTIP) in 500mL of ethanol, and adding a certain amount of 0.1 mol.L^-1The KCl solution is used for initiating a hydrolysis reaction, the stirring is stopped after white precipitation occurs, and the mixture is kept stand for 12 to 48 hours; centrifuging, washing and drying to obtain white TiO₂·nH₂O powder;

(2) 600mg of TiO₂·nH₂O powder was added to a solution containing 60mL of 0.1 mol. L^-10.9mL of hydrogen peroxide with the mass fraction of 3 percent is dripped into the inner liner of the NaOH solution hydrothermal kettle, and the mixture reacts for 2 to 20 hours in a forced air drying oven at the temperature of 140 ℃ and 200 ℃; cooling to room temperature, centrifuging, washing and drying the product to obtain white sodium titanate powder;

(3) adding 1.0g of sodium titanate powder into 250mL of 0.1M dilute hydrochloric acid, fully stirring for 1 hour, and standing for 1 hour; centrifuging, washing and drying the product; calcining the obtained white product in a muffle furnace at 400-500 ℃ for 120min to obtain white TiO₂Mesoporous sphere powder;

(4) 2.425g of Bi (NO)₃)₃·5H₂O was added to 100mL of a 0.4 mol. L solution^-1Fully stirring the solution to obtain a bismuth nitrate solution; 0.585g of NH₄VO₃Adding the mixture into 100mL of 80 ℃ deionized water, fully stirring to obtain an ammonium metavanadate solution, and adding a certain amount of TiO obtained in the step (3)₂The mesoporous spheres are fully stirred, and the bismuth vanadate solution is dripped into the solution; adjusting the pH value of the system to 4 by using ammonia water, and heating and evaporating the mixture in a water bath at 90 ℃ to finally obtain a bright yellow slurry product; washing, centrifuging and drying to obtain bright yellow powder;

(5) calcining the powder obtained in the step (4) in a muffle furnace at the temperature of 400-₄Supported mixed crystalline phase TiO₂A visible light photocatalyst.

2. BiVO of claim 1₄Load(s)Mixed crystal phase TiO₂The preparation method of the visible light catalyst is characterized in that the TiO in the step (4)₂The addition amount of the mesoporous spheres is 0.399-19.968 g.

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