A nanofiber clustered bismuth vanadate gas-sensitive material and preparation method thereof

Abstract

The present invention relates to a nanofiber cluster-shaped bismuth vanadate gas-sensitive material and a preparation method thereof, which is composed of a nanofiber stacked fiber cluster and independently dispersed nanofibers, wherein the diameter of the independently dispersed nanofibers is 5 to 50 nm, the diameter of the nanofiber stacked fiber cluster is 10 to 500 nm, and the nanofibers contain fiber gap micropores less than 2 nm, and the nanofiber stacked fiber clusters and the independently dispersed nanofibers overlap each other to form macropores of 50 to 150 nm. Preparation method: prepare a dilute nitric acid solution; dissolve bismuth nitrate pentahydrate and ammonium metavanadate in the dilute nitric acid solution respectively; add the ammonium metavanadate mixed solution dropwise to the bismuth nitrate mixed solution; add ammonia water; solvent thermal reaction; centrifuge; pour in anhydrous ethanol and rotate and shake; centrifuge and wash. This patented method does not require roasting, has low energy consumption, and is simple in process. The material of the present invention has high sensitivity to ethylene glycol gas, short response recovery time, and low operating temperature.

Description

Technical Field

[0001] The invention belongs to the technical field of metal oxide semiconductor gas-sensitive materials, and in particular relates to a nanofiber clustered bismuth vanadate gas-sensitive material and a preparation method thereof. Background Art

[0002] With the development of social economy, the acceleration of industrialization and urbanization, population growth, environmental pollution and ecological deterioration are becoming increasingly serious. In daily production and life, some volatile organic compounds (VOCs) will be produced, and the increase in VOCs emissions will have an adverse effect on the ambient air. Among them, ethylene glycol (EG), an important industrial raw material, is extremely toxic and can cause great damage to human health. Ethylene glycol is an important organic chemical raw material, mainly used in the production of polyester fibers and antifreeze. With the increase in the production of ethylene glycol in my country, people's health is seriously threatened. The metabolites produced by ethylene glycol after entering the human body are highly toxic, and its metabolites can stimulate the brain and cause diseases such as renal failure. Therefore, it is of great significance to achieve rapid online tracking, detection and early warning of ethylene glycol.

[0003] At present, the methods for detecting toxic and harmful gases include chromatography-mass spectrometry and spectrophotometry. However, these methods are expensive, have a long detection cycle, and are difficult to achieve online real-time monitoring. Metal oxide gas sensors have the advantages of low cost, small size, and the ability to achieve online real-time detection, and are increasingly being used in the detection of harmful gases. The working mechanism of the gas sensor is to convert the concentration change information of the test gas into electrical signal information output, and further detect the target gas by analyzing the changes in the electrical signal information. Research and development of gas sensors with fast response to harmful gases, good selectivity and stability, and excellent performance has far-reaching scientific significance for the detection of harmful gases.

[0004] Bismuth vanadate is an n-type semiconductor oxide, non-toxic and environmentally friendly, and a multi-metal oxide. It has better selectivity and reactivity than single metal oxides, and also shows good sensitivity to ethylene glycol. It is a potential material for constructing bismuth vanadate gas sensors. However, the current bismuth vanadate gas-sensitive materials still have defects such as high operating temperature, low sensitivity at low temperature detection, and long response recovery time. This is extremely unfavorable for the monitoring of toxic gases in the environment. For metal oxide semiconductor gas sensors, their sensing performance is closely related to the carrier transport characteristics, and the microscopic morphology of the material can affect the transport and separation of carriers. The microscopic morphology can be divided into one-dimensional (nanorods, nanofibers), two-dimensional (nanosheets) and three-dimensional (spherical, flower-shaped), among which one-dimensional and two-dimensional low-dimensional materials have a large specific surface area and small size effect. The nanofiber shape can make electrons and holes gather on the side and end of the rod respectively, effectively reducing the carrier recombination rate, and its large aspect ratio also significantly improves the specific surface area and reaction active sites. Therefore, it is an important research direction for gas-sensitive materials to control the structure of pure BiVO4 materials, inhibit the recombination of electrons and holes, and reduce the carrier recombination rate through controllable preparation of micromorphology and defect structure to improve its sensitivity.

[0005] The preparation methods of traditional bismuth vanadate gas-sensitive materials mainly include magnetron sputtering, sol-gel method, hydrothermal method, etc. These methods have the disadvantages of high energy consumption, long time consumption, expensive raw materials, etc., and the sensitivity of the prepared bismuth vanadate gas-sensitive materials is not high enough, and the working temperature range needs to be further expanded. In order to improve the sensitivity of bismuth vanadate gas-sensitive materials, researchers have done a lot of work, such as ion doping, compounding with other metal oxides, and developing new materials. However, doping bismuth vanadate or compounding it with other substances complicates the preparation process, and the process parameters are difficult to control. In order to fundamentally solve the problems of poor sensitivity, slow response recovery, and narrow working temperature range of the current bismuth vanadate gas-sensitive materials, it is necessary to strengthen the development and research of new gas-sensitive materials. Shitu Pei (Journal of Alloys and Compounds 859(2021)158400) disclosed a preparation method and application of a new type of BiVO4 gas-sensitive material. The method uses bismuth nitrate pentahydrate and ammonium metavanadate as initial raw materials, nitric acid as solvent, adjusts the pH of the solution, and adopts a hydrothermal method to prepare a coral-like BiVO4 gas-sensitive material. The preparation process of this method is complicated, and subsequent high-temperature calcination treatment is required, which has high energy consumption and is time-consuming. In addition, the optimal working temperature of the obtained BiVO4 gas-sensitive material for ethylene glycol gas is as high as 340°C. Therefore, it is key to the research to develop a bismuth vanadate material and its preparation method that are more economical and feasible without high-temperature calcination, and to obtain a gas-sensitive material with high sensitivity, fast response and low operating temperature. Summary of the invention

[0006] Purpose of the Invention

[0007] In order to solve the problems existing in the above-mentioned prior art, this patent provides a nanofiber clustered bismuth vanadate gas-sensitive material and a preparation method thereof. The nanofiber clustered bismuth vanadate gas-sensitive material has a small size and a high effective surface area utilization rate. The gas-sensitive element prepared using the nanofiber clustered bismuth vanadate gas-sensitive material has the characteristics of high sensitivity to ethylene glycol gas, low operating temperature and fast response recovery. The preparation process involved is simple and easy to operate, low cost and does not require subsequent high-temperature calcination equipment, and requires little investment.

[0008] Technical Solution

[0009] A nanofiber clustered bismuth vanadate gas-sensitive material, which consists of nanofiber stacked fiber clusters and independently dispersed nanofibers, the independently dispersed nanofibers have a diameter of 5 to 50 nm, the nanofiber stacked fiber clusters have a diameter of 10 to 500 nm, and contain fiber gap micropores less than 2 nm, and the nanofiber stacked fiber clusters and the independently dispersed nanofibers overlap each other to form macropores of 50 to 150 nm.

[0010] Furthermore, 75% to 85% of the nanofiber clustered bismuth vanadate gas-sensitive material is composed of 2 to 12 nanofibers with a length-to-diameter ratio of 8 to 24; 10% to 15% of the nanofiber clustered bismuth vanadate gas-sensitive material is independently dispersed nanofibers with a length-to-diameter ratio of 5 to 24; and 5% to 10% is composed of nanofiber clusters of other numbers with a length-to-diameter ratio of 5 to 24.

[0011] A method for preparing the nanofiber clustered bismuth vanadate gas-sensitive material as described above comprises the following steps:

[0012] Step 1: prepare a dilute nitric acid solution with a concentration of 1 to 4 mol / L;

[0013] Step 2, adding bismuth nitrate pentahydrate and ammonium metavanadate to a dilute nitric acid solution with a concentration of 1 to 4 mol / L, respectively, to obtain a bismuth nitrate mixed solution with a concentration of 0.01 to 0.04 mol / L and an ammonium metavanadate mixed solution with a concentration of 0.01 to 0.04 mol / L, and stirring them uniformly at room temperature to form a colorless clear solution and a light yellow clear solution, respectively;

[0014] Step 3, adding the ammonium metavanadate mixed solution prepared in step 2 dropwise into the bismuth nitrate mixed solution, stirring and mixing at room temperature to obtain a mixed solution of bismuth nitrate and ammonium metavanadate;

[0015] Step 4: adding ammonia water dropwise to the mixed solution of bismuth nitrate and ammonium metavanadate prepared in step 3, adjusting the pH value to 5-6.5, stirring continuously at room temperature to uniformly mix the mixture, and forming a yellow suspension mixed solution;

[0016] Step 5, pouring the yellow suspension mixed solution prepared in step 4 into a Teflon liner, placing it into a reactor, and performing a solvent thermal reaction at a temperature of 150-220° C. and a pressure of 35-40 MPa for 5-18 hours, and naturally cooling it to room temperature to obtain a yellow suspension mixed solution;

[0017] Step 6: Place the yellow suspension mixed solution prepared in step 5 into a centrifuge and centrifuge to obtain a precipitate;

[0018] Step 7: Pour anhydrous ethanol into the precipitate prepared in step 6, place the precipitate into anhydrous ethanol on a pneumatic rotary shaker, and rotate and shake it to make it evenly dispersed in the anhydrous ethanol, so as to be fully washed, and finally obtain a yellow suspension;

[0019] Step 8: Place the yellow suspension prepared in step 7 into a centrifuge for centrifugation to obtain a precipitate. After washing and drying the precipitate, a nanofiber cluster-shaped bismuth vanadate gas-sensitive material is finally obtained.

[0020] Furthermore, in the step 2, the molar ratio of bismuth nitrate pentahydrate to ammonium metavanadate is (1.01-1.2):1.

[0021] Furthermore, in the step 2, the stirring rate of the bismuth nitrate mixed solution and the ammonium metavanadate mixed solution is 400 to 1000 rad / min.

[0022] Furthermore, in the step three, the stirring rate of the mixed solution of bismuth nitrate and ammonium metavanadate is 400 to 1000 rad / min.

[0023] Furthermore, in the step three, the dropwise addition rate of the ammonium metavanadate mixed solution to the bismuth nitrate mixed solution is 0.07 to 0.17 mL / min.

[0024] Furthermore, in step 4, the stirring speed of slowly adding ammonia water dropwise into the mixed solution of bismuth nitrate and ammonium metavanadate is 400 to 1000 rad / min.

[0025] Furthermore, the dropping rate of the ammonia water in step 4 is 0.07-0.17 mL / min.

[0026] Furthermore, in the step eight, an oscillating washing device is used for washing the sediment, and the oscillating washing device includes a fixed platform, a fixed baffle, a fixed vertical plate, a fixed top plate, a motor and an oscillating container. The fixed platform, the fixed baffle and the fixed top plate are fixed on one side of the fixed vertical plate from top to bottom in sequence, and the motor is fixed to the other side of the fixed vertical plate. The motor shaft of the motor passes through the fixed vertical plate and is fixed with a shaft sleeve, a turntable is clamped on the outside of the shaft sleeve, and a bolt is fixed to the position of the turntable near the outer ring, one end of the first connecting rod is rotatably connected to the bolt, and the other end of the first connecting rod is rotatably connected to one end of the third connecting rod and the second connecting rod by a latch at the same time, the other end of the third connecting rod is rotatably connected to the upper end of the fixed platform through a first hinge, and the other end of the second connecting rod is rotatably connected to the lower end of the push rod through a second hinge, the push rod vertically passes through the fixed baffle and has an oscillating container fixed on the upper end, the oscillating container vertically passes through the fixed top plate, a sliding bearing is provided between the oscillating container and the fixed top plate, and a spring is provided on the outer sleeve of the push rod, and the spring is located between the lower end of the oscillating container and the upper end of the fixed baffle.

[0027] Advantages and effects

[0028] The nanofiber clustered bismuth vanadate gas-sensitive material prepared by the present invention has a fibrous morphology that causes electrons to gather at both ends and holes to gather on the fiber sides, effectively improving the carrier separation rate; it has the advantages of small size, large aspect ratio, smooth and flat sides, easy gas adsorption and detachment, high effective surface area utilization, etc. When applied to gas sensors, the sensitivity to ethylene glycol gas is high and the response time is short.

[0029] The present invention uses mechanical shaking instead of manual shaking in the washing method, which saves time and effort. The mechanical vertical shaking can wash the impurities more thoroughly without destroying the material morphology, which is beneficial to the improvement of the gas-sensitive performance of the material.

[0030] The preparation method of the present invention is simple and easy to operate, has low cost, does not require an active agent, is non-toxic and environmentally friendly, and requires little equipment investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. The protection scope of the present invention is not limited to the following description.

[0032] Figure 1 This is a scanning electron microscope (SEM) image of the nanofiber clustered bismuth vanadate gas-sensitive material obtained in Example 2 at a magnification of 1000 times;

[0033] Figure 2 This is a scanning electron microscope (SEM) image of the nanofiber clustered bismuth vanadate gas-sensitive material obtained in Example 2 at a magnification of 6000 times;

[0034] Figure 3This is a scanning electron microscope (SEM) image of the nanofiber clustered bismuth vanadate gas-sensitive material obtained in Example 2 at a magnification of 30,000 times;

[0035] Figure 4 This is a sensitivity diagram of the nanofiber clustered bismuth vanadate gas-sensitive material prepared in Example 2 to 100 ppm ethylene glycol at different temperatures;

[0036] Figure 5 The graph is a dynamic response curve of the nanofiber clustered bismuth vanadate gas-sensitive material prepared in Example 2 to 100 ppm ethylene glycol at different temperatures;

[0037] Figure 6 This is a response recovery time curve of the nanofiber clustered bismuth vanadate gas-sensitive material prepared in Example 2 to 100 ppm ethylene glycol at a temperature of 240° C.;

[0038] Figure 7 This is a scanning electron microscope (SEM) image of the nanofiber clustered bismuth vanadate gas-sensitive material prepared in Example 4;

[0039] Figure 8 It is a schematic diagram of the overall structure of the oscillation washing equipment;

[0040] Fig. 9 It is the structural diagram of the motor and the turntable;

[0041] Fig.10 It is a schematic diagram of the structure of the rotation connection of the first connecting rod, the second connecting rod and the third connecting rod.

[0042] Explanation of the accompanying drawings: 1. fixed platform; 2. first hinge; 3. third connecting rod; 4. latch; 5. second connecting rod; 6. second hinge; 7. spring; 8. sliding bearing; 9. oscillation container; 10. push rod; 11. first connecting rod; 12. turntable; 13. motor shaft; 14. first gasket; 15. bolt; 16. bushing; 17. key; 18. motor; 19. first nut; 20. fixed baffle; 21. second gasket; 22. second nut; 23. third gasket; 24. third nut; 25. fixed vertical plate; 26. fixed top plate. DETAILED DESCRIPTION

[0043] The bismuth nitrate pentahydrate, ammonium metavanadate, nitric acid, ammonia water and ethylene glycol used in the embodiments of the present invention are commercially available analytically pure reagents.

[0044] The gas sensitivity test in the embodiment of the present invention adopts Zhengzhou Weisheng WS-30B gas sensitivity tester.

[0045] In the embodiment of the present invention, a Hitachi SU8010 field emission scanning electron microscope is used for microscopic morphology detection.

[0046] A nanofiber clustered bismuth vanadate gas-sensitive material, which consists of a nanofiber stacked fiber cluster and independently dispersed nanofibers, wherein the diameter of the independently dispersed nanofibers is 5-50nm, the diameter of the nanofiber stacked fiber cluster is 10-500nm, and the nanofibers contain fiber gap micropores less than 2nm, and the nanofiber stacked fiber cluster and the independently dispersed nanofibers overlap each other to form macropores of 50-150nm; 75%-85% of the nanofiber clustered bismuth vanadate gas-sensitive material consists of 2-12 nanofibers, with an aspect ratio of 8-24; 10%-15% of the nanofiber clustered bismuth vanadate gas-sensitive material consists of independently dispersed nanofibers, with an aspect ratio of 5-24; and 5%-10% consists of nanofiber clusters of other numbers (greater than or equal to 13), with an aspect ratio of 5-24.

[0047] The preparation method of nanofiber clustered bismuth vanadate gas-sensitive material comprises the following steps:

[0048] Step 1: Measure a certain amount of concentrated nitric acid and deionized water to prepare a dilute nitric acid solution with a concentration of 1 to 4 mol / L;

[0049] Step 2, weigh a certain amount of bismuth nitrate pentahydrate and ammonium metavanadate, the molar ratio of bismuth nitrate pentahydrate to ammonium metavanadate is (1.01-1.2):1; add bismuth nitrate pentahydrate and ammonium metavanadate to a dilute nitric acid solution with a concentration of 1-4 mol / L, respectively, to obtain a bismuth nitrate mixed solution with a concentration of 0.01-0.04 mol / L and an ammonium metavanadate mixed solution with a concentration of 0.01-0.04 mol / L, and stir at room temperature at a stirring rate of 400-1000 rad / min to form a colorless clear solution and a light yellow clear solution, respectively;

[0050] Step 3, adding the ammonium metavanadate mixed solution prepared in step 2 dropwise into the bismuth nitrate mixed solution at a dropping rate of 0.07 to 0.17 mL / min, stirring and mixing at a stirring rate of 400 to 1000 rad / min at room temperature to obtain a mixed solution of bismuth nitrate and ammonium metavanadate;

[0051] Step 4: measuring a certain amount of ammonia water, adding the ammonia water dropwise to the mixed solution of bismuth nitrate and ammonium metavanadate prepared in step 3, the dropping rate of the ammonia water is 0.07-0.17 mL / min, the pH value is adjusted to 5-6.5, and the stirring rate is 400-1000 rad / min at room temperature to continuously stir and mix the mixture to form a yellow suspension mixed solution;

[0052] Step 5, pouring the yellow suspension mixed solution prepared in step 4 into a Teflon liner, placing it into a reactor, and performing a solvent thermal reaction at a temperature of 150-220° C. and a pressure of 35-40 MPa for 5-18 hours, and naturally cooling it to room temperature to obtain a yellow suspension mixed solution;

[0053] Step 6: Place the yellow suspension mixed solution prepared in step 5 into a centrifuge and centrifuge to obtain a precipitate;

[0054] Step 7: Pour anhydrous ethanol into the precipitate prepared in step 6, place the precipitate into anhydrous ethanol on a pneumatic rotary shaker, and rotate and shake for 5 to 10 minutes to make it evenly dispersed in the anhydrous ethanol and fully washed, and finally obtain a yellow suspension;

[0055] Step 8: Place the yellow suspension prepared in step 7 into a centrifuge for centrifugation to obtain a precipitate. After washing and drying the precipitate, a nanofiber cluster-shaped bismuth vanadate gas-sensitive material is finally obtained.

[0056] like Figure 8 , Fig. 9 and Fig.10As shown, the sediment is washed using an oscillating washing device, which includes a fixed platform 1, a fixed baffle 20, a fixed vertical plate 25, a fixed top plate 26, a motor 18 and an oscillating container 9. The fixed platform 1, the fixed baffle 20 and the fixed top plate 26 are fixed on one side of the fixed vertical plate 25 from top to bottom in sequence, and the motor 18 is fixed to the other side of the fixed vertical plate 25. The motor shaft 13 of the motor 18 passes through the fixed vertical plate 25 and is fixed with a sleeve 16 through a key 17. The sleeve 16 is externally clamped with a turntable 12, and a bolt 15 is fixed to the position of the turntable 12 near the outer ring through a first nut 19. One end of the bolt 15 is rotatably connected to the first connecting rod 11. Preferably, a first gasket 14 is provided between the bolt 15 and the first connecting rod 11 or between the first connecting rod 11 and the turntable 12 to reduce friction. The other end of the first connecting rod 11 is connected to the third connecting rod 3 The second end of the third connecting rod 3 is rotatably connected to the first end of the fixed platform 1 through the first hinge 2, and the other end of the second connecting rod 5 is rotatably connected to the lower end of the push rod 10 through the second hinge 6. The push rod 10 vertically passes through the fixed baffle 20 and an oscillation container 9 is fixed on the upper end. The oscillation container 9 vertically passes through the fixed top plate 26. A sliding bearing 8 is provided between the oscillation container 9 and the fixed top plate 26. The push rod 10 is covered with a spring 7, and the spring 7 is located between the lower end of the oscillation container 9 and the upper end of the fixed baffle 20. The operation of the oscillation washing equipment is as follows: put the sample into the oscillation container 9, start the motor 18, the motor shaft 13 starts to rotate, driving the turntable 12 to rotate, and according to the crank-connecting rod principle, the first connecting rod 11 will drive the third connecting rod 3 and the second connecting rod 5 to rotate and move, so that the third connecting rod 3 and the second connecting rod 5 perform a regular clamping action, and then the push rod 10 moves up and down, so that the oscillation container 9 oscillates up and down, thereby achieving the purpose of fully washing the sample.

[0057] Example 1

[0058] The preparation method of nanofiber clustered bismuth vanadate gas-sensitive material comprises the following steps:

[0059] Step 1: Measure a certain amount of concentrated nitric acid and deionized water to prepare a dilute nitric acid solution with a concentration of 1 mol / L;

[0060] Step 2, weighing a certain amount of bismuth nitrate pentahydrate and ammonium metavanadate, the molar ratio of bismuth nitrate pentahydrate to ammonium metavanadate is 1.01:1; adding bismuth nitrate pentahydrate and ammonium metavanadate to a dilute nitric acid solution with a concentration of 1 mol / L, respectively, to obtain a bismuth nitrate mixed solution with a concentration of 0.01 mol / L and an ammonium metavanadate mixed solution with a concentration of 0.01 mol / L, stirring at a stirring rate of 400 rad / min at room temperature, respectively, to form a colorless clear solution and a light yellow clear solution, respectively;

[0061] Step 3, adding the ammonium metavanadate mixed solution prepared in step 2 dropwise into the bismuth nitrate mixed solution at a dropping rate of 0.07 mL / min, stirring and mixing at a stirring rate of 400 rad / min at room temperature to obtain a mixed solution of bismuth nitrate and ammonium metavanadate;

[0062] Step 4: Measure a certain amount of ammonia water, add the ammonia water dropwise to the mixed solution of bismuth nitrate and ammonium metavanadate prepared in step 3, the dropping rate of the ammonia water is 0.07 mL / min, the pH value is adjusted to 6.5, and the stirring rate is 400 rad / min at room temperature to continuously stir and mix the mixture to form a yellow suspension mixed solution;

[0063] Step 5, pouring the yellow suspension mixed solution prepared in step 4 into a Teflon liner, placing it into a reactor, performing a solvent thermal reaction at a temperature of 150° C. and a pressure of 40 MPa for 18 hours, and naturally cooling to room temperature to obtain a yellow suspension mixed solution;

[0064] Step 6: Place the yellow suspension mixed solution prepared in step 5 into a centrifuge and centrifuge to obtain a precipitate;

[0065] Step 7: Pour anhydrous ethanol into the precipitate prepared in step 6, place the precipitate into anhydrous ethanol on a pneumatic rotary shaker, and rotate and shake for 5 minutes to make it evenly dispersed in the anhydrous ethanol and fully washed, and finally obtain a yellow suspension;

[0066] Step 8: Place the yellow suspension prepared in step 7 into a centrifuge for centrifugation to obtain a precipitate. After washing and drying the precipitate, a nanofiber cluster-shaped bismuth vanadate gas-sensitive material is finally obtained.

[0067] Example 2

[0068] The preparation method of nanofiber clustered bismuth vanadate gas-sensitive material comprises the following steps:

[0069] Step 1: Measure a certain amount of concentrated nitric acid and deionized water to prepare a dilute nitric acid solution with a concentration of 2 mol / L;

[0070] Step 2, weigh a certain amount of bismuth nitrate pentahydrate and ammonium metavanadate, the molar ratio of bismuth nitrate pentahydrate to ammonium metavanadate is 1.1:1; add bismuth nitrate pentahydrate and ammonium metavanadate to a dilute nitric acid solution with a concentration of 2 mol / L, respectively, to obtain a bismuth nitrate mixed solution with a concentration of 0.02 mol / L and an ammonium metavanadate mixed solution with a concentration of 0.02 mol / L, and stir at room temperature at a stirring rate of 600 rad / min to form a colorless clear solution and a light yellow clear solution, respectively;

[0071] Step 3, adding the ammonium metavanadate mixed solution prepared in step 2 dropwise into the bismuth nitrate mixed solution at a dropping rate of 0.1 mL / min, stirring and mixing at a stirring rate of 600 rad / min at room temperature to obtain a mixed solution of bismuth nitrate and ammonium metavanadate;

[0072] Step 4: Measure a certain amount of ammonia water, add the ammonia water dropwise to the mixed solution of bismuth nitrate and ammonium metavanadate prepared in step 3, the ammonia water drop rate is 0.1 mL / min, the pH value is adjusted to 6, and the stirring rate is 600 rad / min at room temperature to continuously stir and mix the mixture to form a yellow suspension mixed solution;

[0073] Step 5, pouring the yellow suspension mixed solution prepared in step 4 into a Teflon liner, placing it into a reactor, performing a solvent thermal reaction at a temperature of 180° C. and a pressure of 38 MPa for 14 h, and naturally cooling it to room temperature to obtain a yellow suspension mixed solution;

[0074] Step 6: Place the yellow suspension mixed solution prepared in step 5 into a centrifuge and centrifuge to obtain a precipitate;

[0075] Step 7: Pour anhydrous ethanol into the precipitate prepared in step 6, place the precipitate into anhydrous ethanol on a pneumatic rotary shaker, and rotate and shake for 6 minutes to make it evenly dispersed in the anhydrous ethanol and fully washed, and finally obtain a yellow suspension;

[0076] Step 8: Place the yellow suspension prepared in step 7 into a centrifuge for centrifugation to obtain a precipitate. After washing and drying the precipitate, a nanofiber cluster-shaped bismuth vanadate gas-sensitive material is finally obtained.

[0077] The scanning electron microscope images of the obtained materials are shown in Figure 1 , Figure 2 , Figure 3 As shown, from Figure 1 , Figure 2 It can be seen that the nano-bismuth vanadate powder prepared by the present invention is in the form of nanofiber clusters, is evenly dispersed, has a diameter of 50 to 500 nm, and an aspect ratio in the range of 8 to 24; Figure 3It can be seen that the nano-bismuth vanadate powder prepared by the present invention is in the form of nanofiber clusters, 85% of which is composed of 5 to 12 nanofibers, and 10% is composed of independently dispersed nanofibers. Figure 4 This is the sensitivity diagram of the prepared nanofiber clustered bismuth vanadate gas-sensitive material to 100ppm ethylene glycol in the working temperature range of 200-300℃. It can be seen from the figure that with the increase of the working temperature, the sensitivity of the prepared gas-sensitive element shows a trend of first increasing and then decreasing. The sensitivity reaches the highest value of 150 at the working temperature of 240℃. Figure 5 The figure is a dynamic curve diagram of the prepared nanofiber clustered bismuth vanadate gas-sensitive material to 100 ppm ethylene glycol at different temperatures. It can be seen from the figure that as the temperature increases, the steady-state voltage and the starting voltage values ​​also increase. Figure 6 This is the voltage dynamic response diagram of the prepared nanofiber clustered bismuth vanadate gas-sensitive material to ethylene glycol at 240°C. It can be seen from the figure that the prepared bismuth vanadate gas-sensitive material has high sensitivity to ethylene glycol gas, and the response time is relatively short, about 47s, and the recovery time is 28s.

[0078] Example 3

[0079] The preparation method of nanofiber clustered bismuth vanadate gas-sensitive material comprises the following steps:

[0080] Step 1: Measure a certain amount of concentrated nitric acid and deionized water to prepare a dilute nitric acid solution with a concentration of 3 mol / L;

[0081] Step 2, weighing a certain amount of bismuth nitrate pentahydrate and ammonium metavanadate, the molar ratio of bismuth nitrate pentahydrate to ammonium metavanadate is 1.15:1; adding bismuth nitrate pentahydrate and ammonium metavanadate to a dilute nitric acid solution with a concentration of 3 mol / L, respectively, to obtain a bismuth nitrate mixed solution with a concentration of 0.03 mol / L and an ammonium metavanadate mixed solution with a concentration of 0.03 mol / L, stirring at a stirring rate of 800 rad / min at room temperature, respectively, to form a colorless clear solution and a light yellow clear solution, respectively;

[0082] Step 3, adding the ammonium metavanadate mixed solution prepared in step 2 dropwise into the bismuth nitrate mixed solution at a dropping rate of 0.14 mL / min, stirring and mixing at a stirring rate of 800 rad / min at room temperature to obtain a mixed solution of bismuth nitrate and ammonium metavanadate;

[0083] Step 4: Measure a certain amount of ammonia water, add the ammonia water dropwise to the mixed solution of bismuth nitrate and ammonium metavanadate prepared in step 3, the dropping rate of the ammonia water is 0.14 mL / min, the pH value is adjusted to 5.5, and the stirring rate is 800 rad / min at room temperature to continuously stir and mix the mixture to form a yellow suspension mixed solution;

[0084] Step 5, pour the yellow suspension mixed solution prepared in step 4 into a Teflon liner, put it into a reactor, perform solvent thermal reaction at a temperature of 200° C. and a pressure of 36 MPa for 10 h, and naturally cool to room temperature to obtain a yellow suspension mixed solution;

[0085] Step 6: Place the yellow suspension mixed solution prepared in step 5 into a centrifuge and centrifuge to obtain a precipitate;

[0086] Step 7: Pour anhydrous ethanol into the precipitate prepared in step 6, place the precipitate into anhydrous ethanol on a pneumatic rotary shaker, and rotate and shake for 8 minutes to make it evenly dispersed in the anhydrous ethanol and fully washed, and finally obtain a yellow suspension;

[0087] Step 8: Place the yellow suspension prepared in step 7 into a centrifuge for centrifugation to obtain a precipitate. After washing and drying the precipitate, a nanofiber cluster-shaped bismuth vanadate gas-sensitive material is finally obtained.

[0088] Example 4

[0089] The preparation method of nanofiber clustered bismuth vanadate gas-sensitive material comprises the following steps:

[0090] Step 1: Measure a certain amount of concentrated nitric acid and deionized water to prepare a dilute nitric acid solution with a concentration of 4 mol / L;

[0091] Step 2, weigh a certain amount of bismuth nitrate pentahydrate and ammonium metavanadate, the molar ratio of bismuth nitrate pentahydrate to ammonium metavanadate is 1.2:1; add bismuth nitrate pentahydrate and ammonium metavanadate to a dilute nitric acid solution with a concentration of 4 mol / L, respectively, to obtain a bismuth nitrate mixed solution with a concentration of 0.04 mol / L and an ammonium metavanadate mixed solution with a concentration of 0.04 mol / L, and stir at room temperature at a stirring rate of 1000 rad / min to form a colorless clear solution and a light yellow clear solution, respectively;

[0092] Step 3, adding the ammonium metavanadate mixed solution prepared in step 2 dropwise into the bismuth nitrate mixed solution at a dropping rate of 0.17 mL / min, stirring and mixing at a stirring rate of 1000 rad / min at room temperature to obtain a mixed solution of bismuth nitrate and ammonium metavanadate;

[0093] Step 4: Measure a certain amount of ammonia water, add the ammonia water dropwise to the mixed solution of bismuth nitrate and ammonium metavanadate prepared in step 3, the dropping rate of the ammonia water is 0.17 mL / min, the pH value is adjusted to 5, and the stirring rate is 1000 rad / min at room temperature to continuously stir and mix them evenly to form a yellow suspension mixed solution;

[0094] Step 5, pour the yellow suspension mixed solution prepared in step 4 into a Teflon liner, put it into a reactor, perform a solvent thermal reaction at a temperature of 220° C. and a pressure of 35 MPa for 5 hours, and naturally cool it to room temperature to obtain a yellow suspension mixed solution;

[0095] Step 6: Place the yellow suspension mixed solution prepared in step 5 into a centrifuge and centrifuge to obtain a precipitate;

[0096] Step 7: Pour anhydrous ethanol into the precipitate prepared in step 6, place the precipitate into anhydrous ethanol on a pneumatic rotary shaker, and rotate and shake for 10 minutes to make it evenly dispersed in the anhydrous ethanol and fully washed, and finally obtain a yellow suspension;

[0097] Step 8: Place the yellow suspension prepared in step 7 into a centrifuge for centrifugation to obtain a precipitate. After washing and drying the precipitate, a nanofiber cluster-shaped bismuth vanadate gas-sensitive material is finally obtained.

[0098] The scanning electron microscope images of the obtained materials are shown in Figure 7 As shown, from Figure 7 It can be seen that the BiVO4 prepared by the present invention is composed of nanoplates and nanoparticles; the edge morphology of the nanoplate is irregular, the thickness is about 100nm, and the size of the nanoparticles is 100-500nm.

[0099] Obviously, the above-mentioned embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the embodiments of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is impossible to list all the embodiments here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing a nanofiber clustered bismuth vanadate gas-sensitive material, characterized in that: The nanofiber clustered bismuth vanadate gas-sensitive material is composed of nanofiber stacked fiber clusters and independently dispersed nanofibers, the diameter of the independently dispersed nanofibers is 5-50nm, the diameter of the nanofiber stacked fiber clusters is 10-500nm, and contains fiber gap micropores less than 2nm, and the nanofiber stacked fiber clusters and the independently dispersed nanofibers overlap each other to form macropores of 50-150nm; 75%-85% of the nanofiber clustered bismuth vanadate gas-sensitive material is composed of 2-12 nanofibers, with an aspect ratio of 8-24; 10%-15% of the nanofiber clustered bismuth vanadate gas-sensitive material is independently dispersed nanofibers, with an aspect ratio of 5-24; 5%-10% is composed of nanofiber clusters of other numbers, with an aspect ratio of 5-24; The steps are as follows: Step 1: prepare a dilute nitric acid solution with a concentration of 1 to 4 mol / L; Step 2, adding bismuth nitrate pentahydrate and ammonium metavanadate to a dilute nitric acid solution with a concentration of 1 to 4 mol / L, respectively, to obtain a bismuth nitrate mixed solution with a concentration of 0.01 to 0.04 mol / L and an ammonium metavanadate mixed solution with a concentration of 0.01 to 0.04 mol / L, and stirring them uniformly at room temperature to form a colorless clear solution and a light yellow clear solution, respectively; Step 3, adding the ammonium metavanadate mixed solution prepared in step 2 dropwise into the bismuth nitrate mixed solution, stirring and mixing at room temperature to obtain a mixed solution of bismuth nitrate and ammonium metavanadate; Step 4: adding ammonia water dropwise to the mixed solution of bismuth nitrate and ammonium metavanadate prepared in step 3, adjusting the pH value to 5-6.5, stirring continuously at room temperature to uniformly mix the mixture, and forming a yellow suspension mixed solution; Step 5, pouring the yellow suspension mixed solution prepared in step 4 into a Teflon liner, placing it into a reactor, and performing a solvent thermal reaction at a temperature of 150-220° C. and a pressure of 35-40 MPa for 5-18 hours, and naturally cooling it to room temperature to obtain a yellow suspension mixed solution; Step 6: Place the yellow suspension mixed solution prepared in step 5 into a centrifuge and centrifuge to obtain a precipitate; Step 7: Pour anhydrous ethanol into the precipitate prepared in step 6, place the precipitate into anhydrous ethanol on a pneumatic rotary shaker, and rotate and shake it to make it evenly dispersed in the anhydrous ethanol, so as to be fully washed, and finally obtain a yellow suspension; Step 8: Place the yellow suspension prepared in step 7 into a centrifuge for centrifugation to obtain a precipitate. After washing and drying the precipitate, a nanofiber cluster-shaped bismuth vanadate gas-sensitive material is finally obtained.

2. The method for preparing the nanofiber clustered bismuth vanadate gas-sensitive material according to claim 1, characterized in that: The molar ratio of bismuth nitrate pentahydrate to ammonium metavanadate in step 2 is (1.01-1.2):

1.

3. The method for preparing the nanofiber clustered bismuth vanadate gas-sensitive material according to claim 1 or 2, characterized in that: The stirring rate of stirring the bismuth nitrate mixed solution and the ammonium metavanadate mixed solution in step 2 is 400-1000 rad / min.

4. The method for preparing the nanofiber clustered bismuth vanadate gas-sensitive material according to claim 1, characterized in that: The stirring rate of the mixed solution of bismuth nitrate and ammonium metavanadate in step 3 is 400-1000 rad / min.

5. The method for preparing the nanofiber clustered bismuth vanadate gas-sensitive material according to claim 1 or 4, characterized in that: In the step 3, the ammonium metavanadate mixed solution is added dropwise to the bismuth nitrate mixed solution at a dropping rate of 0.07 to 0.17 mL / min.

6. The method for preparing the nanofiber clustered bismuth vanadate gas-sensitive material according to claim 1, characterized in that: In the step 4, the ammonia water is slowly added dropwise into the mixed solution of bismuth nitrate and ammonium metavanadate at a stirring speed of 400 to 1000 rad / min.

7. The method for preparing the nanofiber clustered bismuth vanadate gas-sensitive material according to claim 1 or 6, characterized in that: The dropping rate of the ammonia water in the step 4 is 0.07-0.17 mL / min.

8. The method for preparing the nanofiber clustered bismuth vanadate gas-sensitive material according to claim 1, characterized in that: The sediment washing in step eight uses an oscillating washing device, which comprises a fixed platform (1), a fixed baffle (20), a fixed vertical plate (25), a fixed top plate (26), a motor (18) and an oscillating container (9). The fixed platform (1), the fixed baffle (20) and the fixed top plate (26) are fixed on one side of the fixed vertical plate (25) in sequence from top to bottom. The motor (18) is fixed on the other side of the fixed vertical plate (25). The motor shaft (13) of the motor (18) passes through the fixed vertical plate (25) and is fixed with a shaft sleeve (16). The shaft sleeve (16) is externally clamped with a turntable (12). A bolt (15) is fixed at a position close to the outer ring of the turntable (12). One end of the bolt (15) is rotatably connected to the first connecting rod (11). The other end of the connecting rod (11) is rotatably connected to one end of the third connecting rod (3) and the second connecting rod (5) through a latch (4). The other end of the third connecting rod (3) is rotatably connected to the upper end of the fixed platform (1) through a first hinge (2). The other end of the second connecting rod (5) is rotatably connected to the lower end of the push rod (10) through a second hinge (6). The push rod (10) vertically passes through the fixed baffle (20) and an oscillation container (9) is fixed at the upper end. The oscillation container (9) vertically passes through the fixed top plate (26). A sliding bearing (8) is provided between the oscillation container (9) and the fixed top plate (26). The push rod (10) is covered with a spring (7). The spring (7) is located between the lower end of the oscillation container (9) and the upper end of the fixed baffle (20).

Images