Simple preparation method of vanadium oxide catalyst with layered structure
By regulating the heat treatment conditions of vanadium oxide catalysts, forming a layered structure, improving its light absorption capacity and photogenerated electron-hole pair separation efficiency, the problems of poor light absorption capacity and high photogenerated electron-hole pair recombination rate of existing photocatalytic materials are solved, and the efficient photocatalytic degradation of organic wastewater is achieved.
Patent Information
- Application Number
- CN202411753000.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-02
- Publication Date
- 2025-02-28
Smart Images
Figure CN119524833A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a simple preparation method of a layered vanadium oxide catalyst, belonging to the technical field of environmental catalysis. Background Art
[0002] In the process of textile, printing and dyeing industry, with the discharge of industrial wastewater, a large amount of organic dye pollutants that are difficult to degrade also enter the water, soil and atmosphere, seriously polluting the environment. Therefore, it is urgent to develop an efficient catalyst material to eliminate these pollutants.
[0003] Among the numerous photocatalytic materials, nano-oxides have received extensive attention due to their unique size effect and light absorption properties. Many nano-oxides, such as TiO2, ZnO, SnO2 and V2O5, all have photocatalytic activity. However, TiO2, ZnO and SnO2 have large band gaps and poor light absorption capabilities. V2O5 has a smaller band gap, but the photogenerated holes in the material are easily recombined with the photogenerated electrons before they diffuse to the catalyst surface, resulting in an increase in the recombination rate of photogenerated electron-hole pairs. Summary of the invention
[0004] In view of the above problems, the present invention aims to provide a simple preparation method of a layered vanadium oxide catalyst. The preparation method of the present invention is simple, and the surface morphology and structure of the vanadium oxide catalyst material itself are regulated by selecting a suitable heat treatment temperature and time, thereby effectively regulating its light absorption capacity and photogenerated electron-hole pair separation efficiency, and reducing the photogenerated electron-hole pair recombination rate; the layered vanadium oxide catalyst obtained by the present invention can be used for photocatalytic treatment of organic wastewater, and has a high efficiency in degradation of organic pollutants.
[0005] The technical solution of the present invention is specifically described as follows.
[0006] The present invention provides a simple preparation method of a layered vanadium oxide catalyst, wherein the raw material vanadium pentoxide is dissolved in In a hydrogen peroxide solution, the reaction is stirred at room temperature to release gas to form a sol, which is then dried and heat-treated to obtain a vanadium oxide catalyst; wherein the heat treatment temperature is 300-650°C and the heat treatment time is 0.5-4h.
[0007] Preferably, the feeding amount of the raw material vanadium pentoxide is 0.1-0.6 g, the concentration of the hydrogen peroxide solution is 30 wt %, and the hydrogen peroxide solution is 30 mL; the reaction time under stirring at room temperature is 10-30 min.
[0008] Preferably, the drying temperature is 80° C. to 120° C., and the drying time is 2 h to 4 h.
[0009] Preferably, the heat treatment temperature is 350-450°C, and the heat treatment time is 1-2h; more preferably, the heat treatment temperature is 350-400°C, and the heat treatment time is 1h; most preferably, the heat treatment temperature is 350°C, and the heat treatment time is 1h.
[0010] The present invention also provides a layered vanadium oxide catalyst prepared by the simple preparation method, which has a loose layered structure.
[0011] Furthermore, the present invention provides an application of the layered vanadium oxide catalyst in photocatalytic degradation of organic wastewater.
[0012] Preferably, a mercury lamp is used as a light source, and degradation is carried out under the action of ultraviolet light and visible light; the organic pollutants include rhodamine B.
[0013] In the above, the present invention first prepares vanadium oxide sol by a sol-gel method, then dries it to obtain a dry gel, and obtains vanadium oxide catalysts with different morphologies and structures by heat treatment under different conditions. The morphology and structure obtained by heat treatment under appropriate conditions are used to improve the activity of the catalyst, thereby improving the performance of the catalyst as a whole. The vanadium oxide has a loose layered structure, excellent light absorption capacity, and excellent photogenerated charge separation ability. Compared with the prior art, the beneficial effects of the present invention are: The layered vanadium oxide catalyst prepared by the present invention not only has a simple preparation method, but also effectively improves the low photogenerated charge separation efficiency of the traditional vanadium oxide catalyst, thus providing a basis for the practical application of the vanadium oxide catalyst. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 The XRD diagrams of the layered vanadium oxide catalysts and the raw material vanadium pentoxide prepared in Examples 1-7 and Comparative Example 1 are shown.
[0015] Figure 2 These are FESEM images of the layered vanadium oxide catalyst and raw material vanadium pentoxide prepared in Examples 1-7.
[0016] Figure 3 The UV-visible absorption spectra and energy band gaps of the layered vanadium oxide catalysts prepared in Examples 1-7.
[0017] Figure 4 This is the PL spectrum of the layered vanadium oxide catalyst prepared in Example 1-7.
[0018] Figure 5 The photocatalytic degradation activities of different samples and raw material vanadium pentoxide prepared in Examples 1-7. DETAILED DESCRIPTION
[0019] The present invention is further described below by the following embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, but not to limit the present invention.
[0020] In the present disclosure, a layered vanadium oxide catalyst is prepared using commercially available vanadium pentoxide as a raw material. The vanadium oxide is vanadium pentoxide. The XRD pattern and FESEM image of commercially available vanadium pentoxide are shown in Figures 1 and 2. Figure 1 and Figure 2 As shown, the results show that the surface morphology of the raw material vanadium pentoxide is mainly block structure without obvious layered structure; at the same time, the raw material vanadium pentoxide is not completely crystallized.
[0021] In an embodiment of the present invention, a vanadium oxide sol is prepared by a sol-gel method and dried to obtain a vanadium oxide xerogel, which is then subjected to heat treatment under different conditions to obtain a layered vanadium oxide catalyst. The preparation method of the catalyst is exemplified below.
[0022] The vanadium oxide sol is prepared by a sol-gel method, and a layered vanadium oxide catalyst is obtained by drying and subsequent heat treatment. Specifically, a certain amount of commercially available vanadium pentoxide is weighed, a certain amount of hydrogen peroxide solution is measured, the vanadium pentoxide is slowly dissolved in the hydrogen peroxide solution, and the mixture is continuously stirred and reacted vigorously to produce a sol, which is dried at a certain temperature and time to obtain a vanadium oxide dry gel, and then heat treated under certain conditions to obtain a layered vanadium oxide catalyst.
[0023] The following further examples are given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values exemplified below.
[0024] Example 1
[0025] 0.4g of vanadium pentoxide was slowly dissolved in 30mL of 30wt% hydrogen peroxide solution and stirred for 20min at room temperature. A violent reaction occurred, releasing a large amount of gas. After cooling, a reddish-brown sol with high viscosity was obtained. The sol was dried at 100℃ for 4h to obtain vanadium oxide dry gel. The dry gel was scraped off and further heat treated at 350℃ for 1h to obtain a layered vanadium oxide catalyst V2O5-350-1.
[0026] Example 2
[0027] 0.4g of vanadium pentoxide was slowly dissolved in 30mL of 30wt% hydrogen peroxide solution and stirred for 20min at room temperature. A violent reaction occurred, releasing a large amount of gas. After cooling, a reddish-brown sol with high viscosity was obtained. The sol was dried at 100℃ for 4h to obtain vanadium oxide dry gel. The dry gel was scraped off and further heat treated at 450℃ for 1h to obtain a layered vanadium oxide catalyst V2O5-450-1.
[0028] Example 3
[0029] 0.4g of vanadium pentoxide was slowly dissolved in 30mL of 30wt% hydrogen peroxide solution and stirred for 20min at room temperature. A violent reaction occurred, releasing a large amount of gas. After cooling, a reddish-brown sol with high viscosity was obtained. The sol was dried at 100℃ for 4h to obtain vanadium oxide dry gel. The dry gel was scraped off and further heat treated at 550℃ for 1h to obtain a layered vanadium oxide catalyst V2O5-550-1.
[0030] Example 4
[0031] 0.4g of vanadium pentoxide was slowly dissolved in 30mL of 30wt% hydrogen peroxide solution and stirred for 20min at room temperature. A violent reaction occurred, releasing a large amount of gas. After cooling, a reddish-brown sol with high viscosity was obtained. The sol was dried at 100℃ for 4h to obtain vanadium oxide dry gel. The dry gel was scraped off and further heat treated at 650℃ for 1h to obtain a layered vanadium oxide catalyst V2O5-650-1.
[0032] Example 5
[0033] 0.4g of vanadium pentoxide was slowly dissolved in 30mL of 30wt% hydrogen peroxide solution and stirred for 20min at room temperature. A violent reaction occurred, releasing a large amount of gas. After cooling, a reddish-brown sol with high viscosity was obtained. The sol was dried at 100℃ for 4h to obtain vanadium oxide dry gel. The dry gel was scraped off and further heat treated at 350℃ for 2h to obtain a layered vanadium oxide catalyst V2O5-350-2.
[0034] Example 6
[0035] 0.4g of vanadium pentoxide was slowly dissolved in 30mL of 30wt% hydrogen peroxide solution and stirred for 20min at room temperature. A violent reaction occurred, releasing a large amount of gas. After cooling, a reddish-brown sol with high viscosity was obtained. The sol was dried at 100℃ for 4h to obtain vanadium oxide dry gel. The dry gel was scraped off and further heat treated at 350℃ for 3h to obtain a layered vanadium oxide catalyst V2O5-350-3.
[0036] Example 7
[0037] 0.4g of vanadium pentoxide was slowly dissolved in 30mL of 30wt% hydrogen peroxide solution and stirred for 20min at room temperature. A violent reaction occurred, releasing a large amount of gas. After cooling, a reddish-brown sol with high viscosity was obtained. The sol was dried at 100℃ for 4h to obtain vanadium oxide dry gel. The dry gel was scraped off and further heat treated at 350℃ for 4h to obtain a layered vanadium oxide catalyst V2O5-350-4.
[0038] Comparative Example 1
[0039] 0.4g of vanadium pentoxide was slowly dissolved in 30mL of 30wt% hydrogen peroxide solution and stirred for 20min at room temperature. A violent reaction occurred, releasing a large amount of gas. After cooling, a reddish-brown sol with high viscosity was obtained. The sol was dried at 100℃ for 4h to obtain vanadium oxide dry gel. The dry gel was scraped off and further heat treated at 250℃ for 1h to obtain a layered vanadium oxide catalyst V2O5-250-1.
[0040] Performance Testing
[0041] 250 mL of 30wt% sewage solution containing 10 mg / L rhodamine b (RhB) was prepared and added to the photochemical reaction instrument. 15 mg of layered vanadium oxide catalyst was added to the above solution and adsorbed for 30 minutes in a closed light-free environment to reach adsorption saturation, and then its absorbance was measured by UV-visible spectrophotometer to determine the initial concentration of photocatalytic degradation of RhB. At the same time, the oxygen pump was turned on during the stirring process to ensure that there was sufficient dissolved oxygen in the sewage solution for catalytic reaction. After reaching the adsorption-desorption equilibrium, a 300W mercury lamp (working wavelength range of 265.2 nm~579.0 nm) was turned on for photocatalytic degradation reaction. Samples were taken every 20 minutes, and 3 mL was sampled each time. After centrifugation, the supernatant was taken and its absorbance was measured on a UV-visible spectrophotometer to determine the concentration of RhB at different reaction times. Thus, its photocatalytic activity was determined.
[0042] Figure 1 The XRD diagrams of the layered vanadium oxide catalysts and raw material vanadium pentoxide prepared in Examples 1-7 and Comparative Example 1. The characteristic diffraction peaks of the prepared samples at 20.2°, 21.7° and 31° correspond to a-V2O5 (JCPDS NO.41-1426) in the standard spectrum. The raw material vanadium pentoxide and the V2O5-250-1 sample in Comparative Example 1 in the figure are not completely crystallized. As the heat treatment temperature continues to rise and the time continues to extend, the diffraction peak intensity increases, the half-peak width decreases, and the average grain size increases. It suggests that higher heat treatment temperatures and longer times will lead to the growth of material grains.
[0043] Figure 2 The FESEM images of the layered vanadium oxide catalyst and the raw material vanadium pentoxide prepared in Examples 1-7 are shown. It can be found that the surface morphology of the raw material vanadium pentoxide is a block structure without an obvious layered structure. Heat treatment under certain conditions has a significant effect on the material morphology, wherein a lower heat treatment temperature and a shorter time are conducive to the formation of a loose layered vanadium oxide, which can not only increase the specific surface area of the catalyst and expose more active sites, but also help to provide an open space and promote the diffusion and mass transfer of organic macromolecules. At the same time, the loose layered structure also makes it possible to separate photogenerated charges.
[0044] Figure 3 The UV-visible absorption spectrum and energy band gap of the layered vanadium oxide catalyst prepared in Examples 1-7. It can be found that the band gap width of the sample obtained by heat treatment at a higher temperature is smaller, and it is also found that the visible spectrum intensity at 420nm~520nm first increases and then weakens with the increase of temperature. In general, the V2O5-550-1 sample has the best light absorption performance compared with other samples heat treated at different temperatures. Samples heat treated at 350℃ for different times also show a similar trend. This phenomenon may be related to its excellent crystallinity and unique layered structure. However, in general, the effects of heat treatment temperature and heat treatment time on light absorption performance are not very different.
[0045] Figure 4 The PL spectrum of the layered vanadium oxide catalyst prepared in Example 1-7. It can be found that lower heat temperature and shorter heat treatment time are more conducive to improving the separation efficiency of photogenerated charges, which may be closely related to the grain size of the crystal. Under the conditions of lower heat treatment temperature and shorter heat treatment time, it is helpful to form layered vanadium oxide with smaller grain size. The smaller the grain size of the crystal, the faster the diffusion and mass transfer of its active substances, and the photogenerated carriers generated under light radiation can migrate to the surface of the material faster, thereby inhibiting the recombination of photogenerated electrons and holes and improving the photocatalytic activity.
[0046] Figure 5 The photocatalytic degradation activity of the layered vanadium oxide catalyst and the raw material vanadium pentoxide prepared in Example 1-7. The photocatalytic activity of the V2O5-350-1 sample is the best. After the V2O5-350-1 sample is added and irradiated for 40 minutes, the degradation rate of the sample for rhodamine B (RhB) can reach 100%, and the degradation rate constant k is 0.11645 min -1 .
[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art should understand that the specific implementation modes of the present invention can still be modified or replaced by equivalents, and any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims.
Claims
1. A simple preparation method of a layered vanadium oxide catalyst, characterized in that: The raw material vanadium pentoxide is dissolved in a hydrogen peroxide solution, stirred and reacted at room temperature to release gas to form a sol, which is then dried and heat-treated in sequence to obtain a vanadium oxide catalyst; wherein: the heat treatment temperature is 300-650°C and the heat treatment time is 0.5-4h.
2. The simple preparation method according to claim 1, characterized in that: The feeding amount of the raw material vanadium pentoxide is 0.1-0.6 g, the concentration of the hydrogen peroxide solution is 30 wt%, and the hydrogen peroxide solution is 30 mL; the reaction time under normal temperature stirring is 10-30 min.
3. The simple preparation method according to claim 1, characterized in that: The drying temperature is 80℃~120℃ and the drying time is 2h~4h.
4. The simple preparation method according to claim 1, characterized in that: The heat treatment temperature is 350-450°C and the heat treatment time is 1-2h.
5. A layered vanadium oxide catalyst prepared by the simple preparation method according to any one of claims 1 to 4, characterized in that: It has a loose layered structure.
6. Use of the layered vanadium oxide catalyst according to claim 5 in photocatalytic degradation of organic wastewater.
7. The use according to claim 6, characterized in that: Mercury lamp is used as the light source, and degradation is carried out under the action of ultraviolet light and visible light.