A monoclinic BiVO4 nanorod and its efficient synthesis method

Abstract

This invention discloses monoclinic BiVO4 nanorods and a highly efficient synthesis method thereof. The BiVO4 material is prepared by microwave irradiation using analytically pure Bi(NO3)3·5H2O and NH4VO3 as reaction materials, distilled water as solvent, and an ionic liquid (MBIMBr) as surfactant. The microwave irradiation method employed in this patent is simple to operate, energy-concentrated, highly efficient and controllable, energy-saving and environmentally friendly, and beneficial for increasing the reaction rate and yield of the BiVO4 material. XRD and SEM images of the target product fully demonstrate that the preparation method described in this patent can produce BiVO4 materials with regular morphology, high specific surface area, small particle size, and uniform dispersion. The target product, BiVO4 material prepared in this patent, is expected to play an important role in processes such as catalytic degradation of pollutants and catalytic photoelectrochemical water splitting, having far-reaching implications in the field of photocatalysis and possessing potential research and application value.

Description

Technical Field

[0001] The target product of the present invention is mainly used in the field of photocatalytic materials, and particularly relates to a synthesis method for efficiently preparing monoclinic BiVO4 nanorods. Background Art

[0002] With the rapid development of social economy and the acceleration of urbanization, energy consumption and environmental pollution are becoming more and more serious. Therefore, there is an urgent need for an efficient, green and low-cost technology to balance the problems of energy depletion, resource scarcity and environmental degradation caused by the development of human society. Photocatalytic technology has been widely studied in the fields of disinfection, sewage treatment, air purification and water decomposition to produce hydrogen (Maeda K. Photocatalytic water splitting using semiconductor particles: history and recent developments [J]. J. Photochem. Photobiol., C, 2011, 12(4): 237-268) due to its mild reaction conditions, energy conservation and environmental protection, and strong oxidation capacity (Yang Xia. Design and preparation of binary and ternary nanocomposite photocatalytic materials and research on their catalytic behavior [D]. Northeast Normal University, 2009). As a new type of visible light responsive non-TiO2-based photocatalyst that has attracted much attention in recent years, BiVO4 semiconductor materials have great application prospects in the fields of clean energy and environmental governance due to their advantages such as non-toxicity, environmental friendliness, excellent chemical stability, efficient solar energy utilization, narrow band gap of about 2.4 eV and suitable redox potential (Zhou M, Bao J, Xu Y, et al. Photoelectrodes based upon Mo:BiVO4 inverse opals for photoelectrochemical water splitting[J]. ACS Nano, 2014, 8(7): 7088-7098; Liu Jian. Hydrothermal synthesis of BiVO4 powder and study of its photocatalytic performance[J]. Bulletin of the Chinese Ceramic Society, 2015, 34(11): 3394-3397).

[0003] The BiVO4 prepared in the laboratory has a scheelite or zircon structure, which can be divided into three categories: monoclinic scheelite type (sm), tetragonal scheelite type (st) and tetragonal zircon type (zt). Among them, in the monoclinic scheelite BiVO4 crystal structure, Bi 3+ 6s 2Lone pairs of electrons will cause the distortion of Bi-O polyhedrons, which is conducive to the separation and delocalization of photogenerated charges, and has the highest photocatalytic activity among the three crystal forms (JQ Yu, Y. Zhang, A. Kudo. Synthesis and photocatalytic performances of BiVO4 by ammonia co-precipitation process [J]. Journal of Solid State Chemistry, 2009, 182: 223-228). There are many methods for synthesizing BiVO4 materials, such as hydrothermal method, precipitation method, ultrasonic assisted method, etc. (Liu Jingjing, Zhang Zelan, Li Shi, et al. Research progress on modification of bismuth vanadate visible light catalytic materials [J]. Materials Guide, 2021, 35 (17): 17163-17177 + 17184). However, most methods require high temperature and high pressure reaction conditions, and have problems such as long time consumption, significant pollution, high energy consumption, and large product particle size. Summary of the Invention

[0004] The present invention aims to provide an environmentally friendly, time-saving, energy-efficient, energy-concentrated monoclinic BiVO4 nanorod and an efficient synthesis method thereof.

[0005] The present invention is implemented by the following scheme:

[0006] A monoclinic BiVO4 nanorod and an efficient synthesis method thereof, comprising the following steps:

[0007] First, at room temperature, weigh 0.0100-5.0000 g of analytically pure Bi(NO₃)₃·5H₂O and 0.1000-3.0000 g of ionic liquid MBIMBr into a 250 mL beaker, add 5-200 mL of distilled water, stir the solution clockwise with a glass rod for 5-100 min, and then ultrasonicate the solution in an ultrasonic cleaner for 10-60 min to obtain a mixed solution A.

[0008] Second, weigh 0.1000-5.0000 g of analytically pure NH4VO3 into a 100 mL beaker and add 30-90 mL of distilled water. Place the solution in an oven at 60-100°C for 1-5 hours to obtain Solution B.

[0009] Third, the mixed solution A prepared in the first step was transferred to a 500 mL quartz round-bottom flask, and the solution B prepared in the second step was poured into the quartz round-bottom flask containing the mixed solution A to obtain a mixed solution C;

[0010] Fourth, the mixed solution C obtained in the third step was transferred to a microwave reactor equipped with a normal pressure reflux cooling device. The microwave reactor model was a "Midea PJ21C-AU" microwave reactor. The modified power was 200-1400 W and the frequency was 2450 MHz. The heating temperature was set at 80-100 ° C and the reaction time was 10-300 min.

[0011] Fifth, after the reaction is completed, wait for the product obtained in the quartz round-bottom flask to cool naturally to room temperature, transfer the obtained product to a centrifuge, centrifuge at a speed of 4000-10000 rpm for 1-5 minutes, collect the lower layer product, wash it with distilled water 3-5 times, and then wash it with ethanol 3-5 times. Then, place the washed product in an oven and keep it in an oven at 50-80°C for 5-24 hours to obtain the target BiVO4 material.

[0012] The monoclinic BiVO4 nanorod material has a length of 194 to 454 nm and a width of 75 to 182 nm.

[0013] Furthermore, the unit cell parameters of the monoclinic BiVO4 nanorod product are and α=γ=90.0° and β=90.38°, the space group is I2 / a, among which the crystal plane index corresponding to the strongest peak is

[0014] Compared with the prior art, the present invention has the following beneficial technical effects:

[0015] (1) BiVO4 is an n-type semiconductor material with a narrow band gap, non-toxicity, and good physical and chemical stability. It is widely used in the fields of degrading organic pollutants in water, splitting water to produce oxygen, and photocatalysis.

[0016] (2) The microwave radiation method used in this patent is simple to operate and has concentrated energy, which is beneficial to improving the reaction rate and the yield of BiVO4 materials.

[0017] (3) The microwave radiation method involved in the present invention can be used to prepare BiVO4 materials with regular morphology and small particle size, which has the potential for large-scale production and commercialization.

[0018] The microwave radiation method is simple to operate and concentrates energy, which is conducive to improving the reaction rate and the yield of BiVO4 materials; by changing factors such as the molar ratio of the reaction raw materials, the amount of surfactant MBIMBr, the reaction time and the reaction temperature, the micromorphology of the target product BiVO4 material can be precisely controlled, which is conducive to obtaining BiVO4 materials that meet production needs; the target product BiVO4 material prepared by this patent can catalyze the degradation of pollutants and catalyze the photoelectrochemical water decomposition process, which has a far-reaching impact in the field of photocatalysis and has potential research and application value.

[0019] The synthesis process mechanism of the method of the present invention is as follows: the polar ionic liquid (MBIMBr) can be heated in a microwave field through two mechanisms: ion conduction and dipole polarization. It has good microwave absorption effect, strong heat conversion ability and fast heating rate. Under the action of the high-energy microwave field, some precursors react rapidly to form monoclinic bismuth vanadate nanocrystals at a lower temperature, which serve as the crystal nucleus "seed" for material growth. The crystal nucleus "seed" unit can serve as a place for the preferential nucleation and growth of nanocrystals. As the precursor quickly moves toward the dominant crystal plane of the "seed" unit, the growth rate of the crystal along the selected lattice direction is enhanced. In addition, the control of the nanocrystal morphology also benefits from the formation of nanomicelles by surfactant molecules. The morphological growth of the nanocrystal is confined to the entire nanomicelle, thereby developing into a nanorod structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the X-ray diffraction (XRD) pattern of the monoclinic BiVO4 sample when the MBIMBr addition amount is 0.4658 g and the reaction time is 150 min;

[0021] Figure 2 This is the crystal structure diagram of sample 14-0688 phase monoclinic BiVO4;

[0022] Figure 3 This is a 25kx scanning electron microscope (SEM) image of the monoclinic BiVO4 sample with an MBIMBr addition amount of 0.4658 g and a reaction time of 150 min;

[0023] Figure 4 This is a 50kx scanning electron microscope (SEM) image of the monoclinic BiVO4 sample with an MBIMBr addition amount of 0.4658 g and a reaction time of 150 min;

[0024] Figure 5 Schematic diagram of the synthesized morphology of the sample. DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.

[0026] Example 1 Preparation of BiVO4 sample 1 by microwave irradiation

[0027] At room temperature, 2.0615 g of analytically pure Bi(NO3)3·5H2O and 0.4658 g of ionic liquid (MBIMBr) were weighed and placed in a 250 mL beaker, and 115 mL of distilled water was added. After stirring clockwise with a glass rod for 70 min, the solution was placed in an ultrasonic cleaner for ultrasonic treatment for 15 min to obtain a mixed solution A. Subsequently, 0.7457 g of NH4VO3 was weighed and placed in a 100 mL beaker, and 85 mL of distilled water was added thereto. The solution was placed in an oven at 75°C and kept warm for 1 h to obtain a solution B. Subsequently, the mixed solution A was transferred to a 500 mL quartz round-bottom flask, and the solution B was poured into the quartz round-bottom flask containing the mixed solution A to obtain mixed solution C; finally, the mixed solution C was transferred to a microwave reactor equipped with a normal pressure reflux cooling device, the microwave reactor model being a "Midea PJ21C-AU" microwave reactor, the modified power of which was 1000 W and the frequency of which was 2450 MHz; the heating temperature was set to 100°C and the reaction time was set to 150 min; after the reaction was completed, the product obtained in the quartz round-bottom flask was naturally cooled to room temperature, the obtained product was transferred to a centrifuge, and centrifuged at 8000 rpm for 2 min, the lower layer product was taken out, washed with distilled water 3 times, and then washed with ethanol 3 times, and then the washed product was placed in an oven and kept in an oven at 60°C for 24 h to obtain the target BiVO4 material;

[0028] X-ray diffraction (XRD) results show that when the addition amount of MBIMBr is 0.4658 g and the microwave reaction is 150 min, the product is a pure monoclinic BiVO4 phase, and its XRD pattern is as follows: Figure 1 As shown, when 2θ=18.669°, 18.988°, 28.586°, 28.822°, 28.947°, 30.548°, 34.494°, 35.221° and 46.711°, there are characteristic peaks consistent with monoclinic BiVO4 (standard JCPDS card No. 14-0688), and corresponding to (110), (011), (121), (040), (200), (002) and (240) crystal planes, the space group of the product is I2 / a, and the unit cell parameters and α=γ=90.0° and β=90.38°, among which the strongest peak corresponds to The crystal plane has a lattice spacing of 0.309nm and its crystal structure is as follows Figure 2 As shown;

[0029] In addition, the scanning electron microscope SEM images ( Figure 3 、 4 ) shows that the product is composed of stacked nanorods with lengths of 194 to 454 nm and widths of 75 to 182 nm. The schematic diagram of its morphology is shown in Figure 5 As shown;

[0030] The X-ray diffraction test results and scanning electron microscopy (SEM) test results of the product fully demonstrate that the material has a regular morphology and small particle size, and is a functional material with excellent photocatalytic properties.

[0031] Example 2 Preparation of BiVO4 Sample 2 by Microwave Irradiation

[0032] At room temperature, 2.0615 g of analytically pure Bi(NO3)3·5H2O and 0.4658 g of ionic liquid (MBIMBr) were weighed and placed in a 250 mL beaker, and 115 mL of distilled water was added. After stirring clockwise with a glass rod for 70 min, the solution was placed in an ultrasonic cleaner for ultrasonic treatment for 15 min to obtain a mixed solution A; subsequently, 0.7457 g of NH4VO3 was weighed and placed in a 100 mL beaker, and 85 mL of distilled water was added thereto; the solution was placed in an oven at 75°C and kept warm for 1 h to obtain a solution B; then, the mixed solution A was transferred to a 500 mL quartz round-bottom flask, and the solution B was poured into the quartz round-bottom flask containing the mixed solution A to obtain to mixed solution C; finally, the mixed solution C is transferred to a microwave reactor with a normal pressure reflux cooling device, the microwave reactor model is a "Midea PJ21C-AU" microwave reactor, the power of which after modification is 1000 W and the frequency is 2450 MHz; the heating temperature is set to 80°C and the reaction time is set to 10 min; after the reaction is completed, the product obtained in the quartz round-bottom flask is naturally cooled to room temperature, the obtained product is transferred to a centrifuge, and centrifuged at a speed of 8000 rpm for 2 min, the lower layer product is taken out, washed with distilled water 3 times, and then washed with ethanol 3 times, and then the washed product is placed in an oven, and kept in an oven at 60°C for 24 h to obtain the target BiVO4 material.

[0033] Example 3 Preparation of BiVO4 Sample 3 by Microwave Irradiation

[0034] At room temperature, 2.0615 g of analytically pure Bi(NO3)3·5H2O and 0.4658 g of ionic liquid (MBIMBr) were weighed and placed in a 250 mL beaker, and 115 mL of distilled water was added. After stirring clockwise with a glass rod for 70 min, the solution was placed in an ultrasonic cleaner for ultrasonic treatment for 15 min to obtain a mixed solution A. Subsequently, 0.7457 g of NH4VO3 was weighed and placed in a 100 mL beaker, and 85 mL of distilled water was added thereto. The solution was placed in an oven at 75°C and kept warm for 1 h to obtain a solution B. Subsequently, the mixed solution A was transferred to a 500 mL quartz round-bottom flask, and the solution B was poured into the quartz round-bottom flask containing the mixed solution A to obtain mixed solution C; finally, the mixed solution C was transferred to a microwave reactor with a normal pressure reflux cooling device, the microwave reactor model was "Midea PJ21C-AU" microwave reactor, the power after modification was 1000W, and the frequency was 2450MHz; the heating temperature was set to 100°C and the reaction time was set to 300min; after the reaction was completed, the product obtained in the quartz round-bottom flask was naturally cooled to room temperature, the obtained product was transferred to a centrifuge, and centrifuged at 8000rpm for 2min, the lower layer product was taken out, washed with distilled water 3 times, and then washed with ethanol 3 times, and then the washed product was placed in an oven, and kept warm in an oven at 60°C for 24h to obtain the target BiVO4 material.

[0035] To prove the effects achieved by the experimental steps adopted in Examples 1-3 of the present invention, when the operations of Examples 1-3 are not adopted, the products cannot achieve the expected effects and innovations of Examples 1-3 of the present invention.

[0036] Comparative Example of Example 1:

[0037] In (Zhang Xiaojun, Jiao Mengjie, Wang Ning, et al. Preparation of high catalytic efficiency bismuth vanadate visible light catalyst by low temperature hydrothermal method [J]. Journal of Synthetic Crystals, 2016, 45(01): 85-89), Zhang Xiaojun et al. used the hydrothermal method to synthesize BiVO4 material as follows: at room temperature, first weigh 0.9701g Bi(NO3)3·5H2O, add 40mL acetic acid solution (the volume ratio of acetic acid to water is 1:1), and stir with a magnetic stirrer for 20min; secondly, weigh 0.2340g NH4VO3, add 20mL ammonia solution (the volume ratio of ammonia to water is 3:1), and stir for 20min. ) and stirred with a magnetic stirrer for 20 minutes; then, the above solutions were mixed and stirred with a magnetic stirrer for 30 minutes, the pH was adjusted to neutral and the magnetic stirring was continued for 1 hour; finally, the reacted solution was transferred to a stainless steel reactor with a tetrafluoroethylene liner and heated in an 80°C oven for 3 hours; after the reaction, the obtained product was centrifuged, and the precipitate was retained and washed with distilled water and ethanol; the washed product was then dried at 70°C for 12 hours to obtain the target product BiVO4 material; this method cannot prepare high-purity BiVO4 of a single phase, and the obtained product is a microrod with a size of 4 μm.

[0038] The present invention is essentially different from the comparative example, and the present invention is distinctively innovative.

[0039] Comparative Example 2:

[0040] In (Yun Limin, Yang Zhanxu, Shan Shuang, et al. Preparation and photocatalytic performance of bismuth vanadate with different morphologies [J]. New Chemical Materials, 2017, 45(02): 165-167), Yun Limin et al. used a hydrothermal method to synthesize BiVO4 material as follows: at room temperature, first weigh 2.4253g Bi(NO3)3·5H2O, add 5mL 3mol / L HNO3 and 20mL ethylene glycol mixed solution, and stir with a magnetic stirrer for 30min; secondly, weigh 0.5849g NH4VO3, add 20mL dissolved 0.25g SDBS hot water and stirred with a magnetic stirrer for 30 minutes; then, the above solutions were mixed, the pH was adjusted to 2, and the magnetic stirring was continued for 1 hour; finally, the reacted solution was transferred to a 100mL stainless steel reactor with a tetrafluoroethylene liner and heated in an oven at 180°C for 24 hours; after the reaction, the product was washed three times with distilled water and ethanol; then the washed product was dried at 80°C for 12 hours to obtain the target product BiVO4 material; this method cannot prepare high-purity BiVO4 of a single phase, and the obtained product is a micron sphere with a size of 1.2μm.

[0041] There is an essential difference between the patent of the present invention and the comparative example, and the patent of the present invention has distinct innovation.

[0042] Comparative Example of Example 3:

[0043] In (Shen Qianli, Lou Zhengsong. Study on hydrothermal synthesis of bismuth vanadate and photocatalytic degradation of rhodamine B [J]. Journal of Jiangsu University of Science and Technology, 2017, 23(06): 35-39), Shen Qianli et al. used the hydrothermal method to synthesize BiVO4 material as follows: at room temperature, first weigh 0.485g Bi(NO3)3·5H2O and add it to a stainless steel reactor with a tetrafluoroethylene lining, and add an appropriate amount of concentrated HNO3 solution to the reactor. After it is dissolved, add 0.8g oleylamine, 1.2g oleic acid, 5g anhydrous ethanol and an appropriate amount of distilled water. The mixture was stirred evenly using a magnetic stirrer; secondly, 0.117 g of NH4VO3 was weighed and added to the reactor, mixed evenly, and the pH was adjusted to 2.2; then, the reactor was placed in an oven and heated until the solution reaction was completed; after the reaction, the product was centrifuged in a centrifuge at 4000 r / min, and the precipitate was retained and washed four times with distilled water and ethanol; the washed product was then dried at 80°C to obtain the target product BiVO4 material; this method cannot prepare high-purity BiVO4 of a single phase, and the obtained product is micron blocks with a size of 0.7 to 2 μm.

[0044] There is an essential difference between the patent of the present invention and the comparative example, and the patent of the present invention has distinct innovation.

Claims

1. A method for synthesizing monoclinic BiVO4 nanorods, characterized in that The following steps are involved: First, at room temperature, weigh 2.0615 g of analytically pure Bi(NO₃)₃·5H₂O and 0.4658 g of ionic liquid MBIMBr into a 250 mL beaker, add 115 mL of distilled water, stir clockwise with a glass rod for 70 min, and then place the solution in an ultrasonic cleaner for 15 min to obtain mixed solution A. Second, weigh 0.7457 g of analytical grade NH4VO3 into a 100 mL beaker and add 85 mL of distilled water. Place the solution in an oven at 75°C for 1 hour to obtain Solution B. Third, the mixed solution A prepared in the first step was transferred to a 500 mL quartz round-bottom flask, and the solution B prepared in the second step was poured into the quartz round-bottom flask containing the mixed solution A to obtain a mixed solution C; Fourth, the mixed solution C obtained in the third step was transferred to a microwave reactor equipped with a normal pressure reflux cooling device. The microwave reactor model was a "Midea PJ21C-AU" microwave reactor with a modified power of 1000 W and a frequency of 2450 MHz. The heating temperature was set to 100° C. and the reaction time was set to 150 min. Fifth, after the reaction is completed, the product in the quartz round-bottom flask is naturally cooled to room temperature, and the product is transferred to a centrifuge and centrifuged at 8000 rpm for 2 minutes. The lower layer of product is collected, washed three times with distilled water, and then washed three times with ethanol. The washed product is then placed in an oven and kept at 60°C for 24 hours to obtain monoclinic BiVO4 nanorods. The nanorods have a length of 194-454 nm and a width of 75-182 nm; The unit cell parameters of the nanorods are a=5.195Å, b=11.701Å and c=5.092Å, α=γ=90.0° and β=90.38°, and the space group is I2 / a, where the strongest peak corresponds to the crystal plane index .

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