Non-uniform tungsten oxide nanosheet with hierarchical structure and preparation method thereof
By preparing non-uniform tungsten oxide nanosheets with hierarchical structure, the agglomeration problem caused by particle size uniformity of nanotungsten oxide materials is solved, and its application performance in the field of photoelectricity is improved, especially in electrode materials.
Patent Information
- Application Number
- CN202411403652.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-09
- Publication Date
- 2025-01-17
AI Technical Summary
The existing nanotungsten oxide materials have agglomeration due to particle size uniformity and reduce active sites, which limits their application in the field of photoelectricity.
Using a preparation method of non-uniform tungsten oxide nanosheets with a hierarchical structure, the tungsten oxide nanosheets with a hierarchical structure are formed by dropping the ammonium tungstate solution into hydrochloric acid, and stirring and calcining under different conditions to reduce agglomeration. and increase the specific surface area.
The prepared tungsten oxide nanosheets have high specific surface area and surface activity, and can relieve structural stress through hierarchical structures, improving their application performance in the field of photoelectricity, especially in the field of electrode materials.
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Figure CN119320173A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of nano materials, and specifically relates to a non-uniform tungsten oxide nanosheet with a hierarchical structure and a preparation method thereof. Background Art
[0002] Among many semiconductor materials, two-dimensional nano tungsten oxide (WO3) has attracted the attention of researchers due to its unique ion embedding / de-embedding channel. Two-dimensional nano tungsten oxide material is a new type of material with unique structure and excellent performance. One of its three dimensions is between 0.1 and 100 nm, and the other two dimensions are larger than 100 nm. Therefore, it is also called tungsten oxide nanosheets. Nano tungsten oxide has a large specific surface area, high surface energy, and many active sites, which makes it easy to be modified, greatly improving the light absorption and charge transfer efficiency, and is widely used in the optoelectronic field. At the same time, tungsten oxide nanosheets have extremely broad prospects in the direction of new batteries due to their unique electronic effects and high stability. However, nanomaterials with uniform particle size are very easy to agglomerate, which increases the particle size of the material, resulting in a reduction in the active sites that can participate in the reaction, which is not conducive to its industrial application. Summary of the invention
[0003] In order to solve the problems existing in the prior art, the main purpose of the present invention is to provide a non-uniform tungsten oxide nanosheet with a hierarchical structure and a preparation method thereof.
[0004] To solve the above technical problems, according to one aspect of the present invention, the present invention provides the following technical solutions:
[0005] A method for preparing a non-uniform tungsten oxide nanosheet with a hierarchical structure comprises the following steps:
[0006] S1. Take ammonium tungstate solution for later use;
[0007] S2, take hydrochloric acid for use;
[0008] S3, adding the reserved ammonium tungstate solution dropwise to the reserved hydrochloric acid, stirring while dropping; stopping the dropping after a period of time, and continuously stirring during the period of stopping the dropping; repeating the "dropping-stopping the dropping" method until all the reserved ammonium tungstate solution is dropped, to obtain tungstic acid;
[0009] S4, filtering and washing the tungstic acid, and then drying;
[0010] S5. calcining the dried tungstic acid to obtain non-uniform tungsten oxide nanosheets with a hierarchical structure.
[0011] As a preferred embodiment of the method for preparing a non-uniform tungsten oxide nanosheet with a hierarchical structure described in the present invention, wherein: in the step S1, the concentration of the ammonium tungstate solution is 250-300 g / L, calculated as tungsten trioxide.
[0012] As a preferred embodiment of the method for preparing a non-uniform tungsten oxide nanosheet with a hierarchical structure described in the present invention, in step S2, the reserve amount of hydrochloric acid is 1.3 to 1.7 times the theoretical amount of hydrochloric acid required for preparing tungstic acid.
[0013] As a preferred embodiment of the method for preparing the non-uniform tungsten oxide nanosheets with a hierarchical structure described in the present invention, wherein: in the step S2, the concentration of the hydrochloric acid is 16-24wt%.
[0014] As a preferred embodiment of the method for preparing the non-uniform tungsten oxide nanosheets with a hierarchical structure described in the present invention, wherein: in the step S3, the stirring speed is 180-260 r / min.
[0015] As a preferred embodiment of the method for preparing the non-uniform tungsten oxide nanosheets with a hierarchical structure described in the present invention, wherein: in the step S3, the dropping speed of the ammonium tungstate solution is 25-100 mL / min.
[0016] As a preferred embodiment of the method for preparing the non-uniform tungsten oxide nanosheets with a hierarchical structure described in the present invention, wherein: in the step S3, the time for each dropping is 5 to 15 minutes.
[0017] As a preferred embodiment of the method for preparing a non-uniform tungsten oxide nanosheet with a hierarchical structure described in the present invention, wherein: in the step S3, the time for stopping the dripping each time is 5 to 15 minutes.
[0018] As a preferred embodiment of the method for preparing a non-uniform tungsten oxide nanosheet with a hierarchical structure described in the present invention, wherein: in the step S4, the tungstic acid is washed with pure water, and the drying temperature is 110-130°C.
[0019] As a preferred embodiment of the method for preparing a non-uniform tungsten oxide nanosheet with a hierarchical structure described in the present invention, wherein: in the step S5, the calcination temperature is 600-700° C., and the calcination time is 1-2 hours.
[0020] To solve the above technical problem, according to another aspect of the present invention, the present invention provides the following technical solution:
[0021] A non-uniform tungsten oxide nanosheet with a hierarchical structure is prepared by using the method for preparing the non-uniform tungsten oxide nanosheet with a hierarchical structure.
[0022] As a preferred embodiment of the non-uniform tungsten oxide nanosheets with a hierarchical structure described in the present invention, the non-uniform tungsten oxide nanosheets with a hierarchical structure are combined to form a hierarchical structure at the micron level, and the specific surface area is 17 to 21 m 2 / g.
[0023] To solve the above technical problem, according to another aspect of the present invention, the present invention provides the following technical solution:
[0024] An application of the above-mentioned non-uniform tungsten oxide nanosheets with a hierarchical structure in the field of optoelectronics, especially in the field of electrode materials.
[0025] The beneficial effects of the present invention are as follows:
[0026] The present invention provides a non-uniform tungsten oxide nanosheet with a hierarchical structure and a preparation method thereof. The prepared tungsten oxide nanosheet has a large specific surface area and a high surface activity; the tungsten oxide nanosheet is non-uniformly distributed at the microscopic level, and the non-uniform tungsten oxide nanosheet with a hierarchical structure is coupled with each other, which can reduce agglomeration to a certain extent; the tungsten oxide nanosheets are combined to construct a hierarchical structure at the micron level, which makes the material have abundant pores and can alleviate the volume change caused by the structural stress generated inside the material during the reaction process, which is beneficial to its application in the optoelectronic field, especially in the field of electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.
[0028] Figure 1 This is a SEM image of the non-uniform tungsten oxide nanosheets with a hierarchical structure prepared in Example 1 of the present invention.
[0029] Figure 2 for Figure 1 A magnified view of the middle area.
[0030] Figure 3 This is a SEM image of the non-uniform tungsten oxide nanosheets with a hierarchical structure prepared in Example 2 of the present invention.
[0031] Figure 4 for Figure 3 A magnified view of the middle area.
[0032] Figure 5 This is a SEM image of tungsten oxide prepared in Comparative Example 1 of the present invention.
[0033] Figure 6 for Figure 5 A magnified view of the middle area.
[0034] Figure 7 This is a SEM image of tungsten oxide prepared in Comparative Example 2 of the present invention.
[0035] Figure 8 for Figure 7 A magnified view of the middle area.
[0036] Fig. 9 This is a SEM image of tungsten oxide prepared in Comparative Example 3 of the present invention.
[0037] Fig.10 for Fig. 9 A magnified view of the middle area.
[0038] Fig.11 This is a SEM image of tungsten oxide prepared in Comparative Example 4 of the present invention.
[0039] Fig.12 for Fig.11 A magnified view of the middle area.
[0040] Fig.13 This is a SEM image of tungsten oxide prepared in Comparative Example 5 of the present invention.
[0041] Fig.14 for Figure 7 A magnified view of the middle area.
[0042] Fig.15 This is a SEM image of tungsten oxide prepared in Comparative Example 6 of the present invention.
[0043] Fig.16 This is a SEM image of tungsten oxide prepared in Comparative Example 7 of the present invention.
[0044] The realization of the effects, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION
[0045] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0046] Inhomogeneous nanomaterials can achieve high material performance to a certain extent through the reasonable coupling of micro-nanoscale structures. Hierarchical structure materials refer to multi-level materials composed of low-dimensional nanomaterials (nanoparticles / wires / rods / tubes / sheets, etc.) as basic structural units. A major advantage of hierarchical structure materials is that they can reduce agglomeration and expose more surface active sites of the material; and studies have shown that adding hierarchical structure materials to electrode materials can effectively alleviate the volume expansion of the battery during charging and discharging, and extend the battery life.
[0047] According to one aspect of the present invention, the present invention provides the following technical solution:
[0048] A method for preparing a non-uniform tungsten oxide nanosheet with a hierarchical structure comprises the following steps:
[0049] S1. Take ammonium tungstate solution for later use;
[0050] S2, take hydrochloric acid for use;
[0051] S3, adding the reserved ammonium tungstate solution dropwise to the reserved hydrochloric acid, stirring while dropping; stopping the dropping after a period of time, and continuously stirring during the period of stopping the dropping; repeating the "dropping-stopping the dropping" method until all the reserved ammonium tungstate solution is dropped, to obtain tungstic acid;
[0052] S4, filtering and washing the tungstic acid, and then drying;
[0053] S5. calcining the dried tungstic acid to obtain non-uniform tungsten oxide nanosheets with a hierarchical structure.
[0054] Preferably, in step S1, the concentration of the ammonium tungstate solution is 250-300 g / L, calculated as tungsten trioxide. If the concentration of the ammonium tungstate solution is too high, APT is easily precipitated, resulting in impure products and interference with the morphology and particle size of the tungsten oxide obtained by subsequent calcination. If the concentration is too low, the generated tungstic acid crystal nuclei cannot grow normally, and ultimately the ideal tungsten oxide product cannot be obtained. Specifically, in terms of tungsten trioxide, the concentration of the ammonium tungstate solution can be, for example, any one of 250 g / L, 260 g / L, 270 g / L, 280 g / L, 290 g / L, 300 g / L, or a range between any two of them.
[0055] Preferably, in step S2, the amount of hydrochloric acid is 1.3 to 1.7 times the theoretical amount of hydrochloric acid required for preparing tungstic acid, and the concentration of hydrochloric acid is 16 to 24 wt%. When preparing tungstic acid, a precursor of tungsten oxide, the acid concentration directly affects the reaction rate. If the acid concentration is too high, the reaction rate is too fast, which makes the local concentration of ammonium tungstate too high, and the ammonium tungstate completes the reaction without being stirred and dispersed, generating tungstic acid with too large particle size; if the acid concentration is too low, the pH value for generating yellow tungstic acid cannot be reached. Specifically, the amount of hydrochloric acid can be, for example, 1.3 times, 1.4 times, 1.5 times, 1.6 times, 1.7 times the theoretical amount of hydrochloric acid required for preparing tungstic acid, any one of them or a range between any two of them, and the concentration of hydrochloric acid can be, for example, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt% or a range between any two of them.
[0056] Preferably, in step S3, the stirring speed is 180-260 r / min. Too fast a stirring speed will break the grown crystals, while too slow a stirring speed will easily cause the products to pile up and agglomerate, which is not conducive to the crystallization of tungstic acid. Specifically, the stirring speed can be, for example, any one of 180 r / min, 190 r / min, 200 r / min, 210 r / min, 220 r / min, 230 r / min, 240 r / min, 250 r / min, 260 r / min or a range between any two thereof.
[0057] Preferably, in step S3, the dripping speed of the ammonium tungstate solution is 25-100 mL / min, the time of each dripping is 5-15 min, and the time of stopping dripping is 5-15 min each time. The number of repetitions of the "drip-stop dripping" method is 4-12 times. The intermittent dripping method can utilize the principle of intermittent crystallization to make different batches of products have differences in grain size. This is mainly caused by the supersaturation in the solution changing from high to low. When the solution is highly supersaturated, the crystal may tend to form a large number of crystal nuclei rather than promote crystal growth, or it may tend to only generate a small amount of crystal nuclei and promote crystal growth. This is related to the dripping rate and the intermittent time, so it is necessary to select a suitable dripping rate and intermittent time. Specifically, the dropping speed of the ammonium tungstate solution can be, for example, any one of 25 mL / min, 50 mL / min, 75 mL / min, 100 mL / min, or a range between any two of them, the time of each dropping can be, for example, any one of 5 min, 7 min, 10 min, 12 min, 15 min, or a range between any two of them, and the time of stopping the dropping each time can be, for example, any one of 5 min, 7 min, 10 min, 12 min, 15 min, or a range between any two of them.
[0058] Preferably, in step S4, the tungstic acid is washed with pure water and the drying temperature is 110-130° C. The boiling point of hydrochloric acid is 108° C. The high temperature of 110° C. or higher during drying can more thoroughly remove the hydrochloric acid remaining in the washed tungstic acid; however, too high a temperature will make the dried tungstic acid harder and less likely to break, so a temperature suitable for actual production needs is selected between 110° C. and 130° C.
[0059] Preferably, in step S5, the calcination temperature is 600-700°C and the calcination time is 1-2h. The particle surface of tungstic acid, as the precursor of tungsten oxide nanosheets, calcined at high temperature has high activity. Too high calcination temperature and too long calcination time can easily cause the atoms on the surface of the grains to diffuse to the surface of adjacent grains and bond with the corresponding atoms to form stable chemical bonds, resulting in secondary agglomeration and loss of the nanostructure of the material; too low temperature and too short calcination time will cause incomplete calcination and fail to completely convert tungstic acid into tungsten oxide. Therefore, selecting a calcination temperature of 600-700°C and a calcination time of 1-2h can completely oxidize the precursor tungstic acid into highly active tungsten oxide nanosheets and prevent secondary agglomeration of tungsten oxide. Specifically, the calcination temperature can be, for example, any one of 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, or a range between any two of them, and the calcination time can be, for example, any one of 1h, 1h15min, 1h30min, 1h45min, 2h, or a range between any two of them.
[0060] According to another aspect of the present invention, the present invention provides the following technical solution:
[0061] A non-uniform tungsten oxide nanosheet with a hierarchical structure is prepared by the above-mentioned preparation method of the non-uniform tungsten oxide nanosheet with a hierarchical structure, wherein the non-uniform tungsten oxide nanosheet with a hierarchical structure is combined at the micron level to construct a hierarchical structure, and the specific surface area is 17 to 21 m 2 / g.
[0062] The technical solution of the present invention is further described below in conjunction with specific embodiments.
[0063] Example 1
[0064] A method for preparing a non-uniform tungsten oxide nanosheet with a hierarchical structure comprises the following steps:
[0065] S1. Take 3L of ammonium tungstate solution for standby use; the concentration of the ammonium tungstate solution is 260g / L in terms of tungsten trioxide;
[0066] S2, taking hydrochloric acid for standby; the standby amount of the hydrochloric acid is 1.4 times the theoretical amount of hydrochloric acid required for preparing tungstic acid, and the concentration of the hydrochloric acid is 18wt%;
[0067] S3, adding the reserved ammonium tungstate solution dropwise to the reserved hydrochloric acid, stirring while dropping; stopping the dropping after a period of time, and stirring continuously during the stopping of the dropping; repeating the "dropping-stop dropping" method until the reserved ammonium tungstate solution is completely dropped to obtain tungstic acid; the stirring speed is 200r / min, the dropping speed of the ammonium tungstate solution is 50mL / min, the time of each dropping is 10min, the time of each stopping of dropping is 10min, and the number of repetitions of the "dropping-stop dropping" method is 6 times;
[0068] S4, filter and wash the tungstic acid, and then dry it; wash the tungstic acid with pure water, and the drying temperature is 120°C;
[0069] S5, calcining the dried tungstic acid at a temperature of 600° C. for 1 h to obtain a non-uniform tungsten oxide nanosheet having a hierarchical structure, such as Figure 1-2 As shown in the figure, the prepared tungsten oxide nanosheets contain two sizes of non-uniform tungsten oxide sheets, and their thickness is less than 100nm, which belongs to nanostructured materials; the two sizes of tungsten oxide nanosheets build a hierarchical structure at the micron level; its specific surface area BET is 20.86m 2 / g.
[0070] Example 2
[0071] A method for preparing a non-uniform tungsten oxide nanosheet with a hierarchical structure comprises the following steps:
[0072] S1. Take 3L of ammonium tungstate solution for standby use; the concentration of the ammonium tungstate solution is 250g / L in terms of tungsten trioxide;
[0073] S2, taking hydrochloric acid for standby; the standby amount of the hydrochloric acid is 1.5 times the theoretical amount of hydrochloric acid required for preparing tungstic acid, and the concentration of the hydrochloric acid is 20wt%;
[0074] S3, drop the reserved ammonium tungstate solution into the reserved hydrochloric acid, stirring while dropping; stop dropping after a period of time, and continue stirring during the stop dropping; repeat the "dropping-stop dropping" method until the reserved ammonium tungstate solution is completely dropped to obtain tungstic acid; the stirring speed is 180r / min, the dropping speed of the ammonium tungstate solution is 60mL / min, the time of each dropping is 5min, the time of each stopping dropping is 10min, and the number of repetitions of the "dropping-stop dropping" method is 10 times;
[0075] S4, filter and wash the tungstic acid, and then dry it; wash the tungstic acid with pure water, and the drying temperature is 120°C;
[0076] S5, calcining the dried tungstic acid at a temperature of 650° C. for 1.5 h to obtain a non-uniform tungsten oxide nanosheet having a hierarchical structure, such as Figure 3-4 As shown in the figure, the prepared tungsten oxide nanosheets contain two sizes of non-uniform tungsten oxide sheets, and their thickness is less than 100nm, which belongs to nanostructured materials; the two sizes of tungsten oxide nanosheets build a hierarchical structure at the micron level; its specific surface area BET is 18.03m 2 / g.
[0077] Example 3
[0078] A method for preparing a non-uniform tungsten oxide nanosheet with a hierarchical structure comprises the following steps:
[0079] S1. Take 3L of ammonium tungstate solution for standby use; the concentration of the ammonium tungstate solution is 280g / L in terms of tungsten trioxide;
[0080] S2, taking hydrochloric acid for standby; the standby amount of the hydrochloric acid is 1.3 times the theoretical amount of hydrochloric acid required for preparing tungstic acid, and the concentration of the hydrochloric acid is 16wt%;
[0081] S3, drop the reserved ammonium tungstate solution into the reserved hydrochloric acid, stirring while dropping; stop dropping after a period of time, and continue stirring during the stop dropping; repeat the "dropping-stop dropping" method until the reserved ammonium tungstate solution is completely dropped to obtain tungstic acid; the stirring speed is 240r / min, the dropping speed of the ammonium tungstate solution is 50mL / min, the time of each dropping is 6min, the time of each stopping dropping is 10min, and the number of repetitions of the "dropping-stop dropping" method is 10 times;
[0082] S4, filter and wash the tungstic acid, and then dry it; wash the tungstic acid with pure water, and the drying temperature is 130°C;
[0083] S5. The dried tungstic acid was calcined at 650°C for 1 hour to obtain a non-uniform tungsten oxide nanosheet with a hierarchical structure. The non-uniform tungsten oxide nanosheets contained two sizes of non-uniform tungsten oxide sheets, and their thickness was less than 100nm, which belonged to nanostructured materials. The two sizes of tungsten oxide nanosheets constructed a hierarchical structure at the micron level; the specific surface area BET was 18.79m 2 / g.
[0084] Example 4
[0085] A method for preparing a non-uniform tungsten oxide nanosheet with a hierarchical structure comprises the following steps:
[0086] S1. Take 3L of ammonium tungstate solution for standby use; the concentration of the ammonium tungstate solution is 290g / L in terms of tungsten trioxide;
[0087] S2, taking hydrochloric acid for standby; the standby amount of the hydrochloric acid is 1.5 times the theoretical amount of hydrochloric acid required for preparing tungstic acid, and the concentration of the hydrochloric acid is 22wt%;
[0088] S3, adding the reserved ammonium tungstate solution dropwise to the reserved hydrochloric acid, stirring while dropping; stopping the dropping after a period of time, and stirring continuously during the stopping of the dropping; repeating the "dropping-stop dropping" method until the reserved ammonium tungstate solution is completely dropped to obtain tungstic acid; the stirring speed is 260r / min, the dropping speed of the ammonium tungstate solution is 80mL / min, the time of each dropping is 7.5min, the time of each stopping of dropping is 5min, and the number of repetitions of the "dropping-stop dropping" method is 5 times;
[0089] S4, filter and wash the tungstic acid, and then dry it; wash the tungstic acid with pure water, and the drying temperature is 120°C;
[0090] S5. The dried tungstic acid was calcined at 600°C for 1.5 hours to obtain non-uniform tungsten oxide nanosheets with a hierarchical structure. The non-uniform tungsten oxide nanosheets contained two sizes of non-uniform tungsten oxide sheets, and their thickness was less than 100nm, which belonged to nanostructured materials. The two sizes of tungsten oxide nanosheets constructed a hierarchical structure at the micron level; the specific surface area BET was 17.99m 2 / g.
[0091] Example 5
[0092] A method for preparing a non-uniform tungsten oxide nanosheet with a hierarchical structure comprises the following steps:
[0093] S1. Take 3L of ammonium tungstate solution for standby use; the concentration of the ammonium tungstate solution is 300g / L in terms of tungsten trioxide;
[0094] S2, taking hydrochloric acid for standby; the standby amount of the hydrochloric acid is 1.7 times the theoretical amount of hydrochloric acid required for preparing tungstic acid, and the concentration of the hydrochloric acid is 24wt%;
[0095] S3, adding the reserved ammonium tungstate solution dropwise to the reserved hydrochloric acid, stirring while dropping; stopping the dropping after a period of time, and stirring continuously during the stopping of the dropping; repeating the "dropping-stop dropping" method until the reserved ammonium tungstate solution is completely dropped to obtain tungstic acid; the stirring speed is 240r / min, the dropping speed of the ammonium tungstate solution is 100mL / min, the time of each dropping is 15min, the time of each stopping of dropping is 15min, and the number of repetitions of the "dropping-stop dropping" method is 2 times;
[0096] S4, filter and wash the tungstic acid, and then dry it; wash the tungstic acid with pure water, and the drying temperature is 110°C;
[0097] S5. The dried tungstic acid was calcined at 650°C for 1 hour to obtain a non-uniform tungsten oxide nanosheet with a hierarchical structure. The non-uniform tungsten oxide nanosheets contained two sizes of non-uniform tungsten oxide sheets, and their thickness was less than 100nm, which belonged to nanostructured materials. The two sizes of tungsten oxide nanosheets constructed a hierarchical structure at the micron level; the specific surface area BET was 17.08m 2 / g.
[0098] Comparative Example 1
[0099] A method for preparing tungsten oxide comprises the following steps:
[0100] S1. Take 3L of ammonium tungstate solution for standby use; the concentration of the ammonium tungstate solution is 200g / L in terms of tungsten trioxide;
[0101] S2, taking hydrochloric acid for standby; the standby amount of the hydrochloric acid is 1.4 times the theoretical amount of hydrochloric acid required for preparing tungstic acid, and the concentration of the hydrochloric acid is 18wt%;
[0102] S3, dropwise add the reserved ammonium tungstate solution into the reserved hydrochloric acid, stirring while dropping, until the reserved ammonium tungstate solution is completely dropped, to obtain tungstic acid; the stirring speed is 200r / min, and the dropping speed of the ammonium tungstate solution is 50mL / min;
[0103] S4, filter and wash the tungstic acid, and then dry it; wash the tungstic acid with pure water, and the drying temperature is 120°C;
[0104] S5, calcining the dried tungstic acid at a temperature of 600°C for 1 hour to obtain tungsten oxide, such as Figure 5-6 As shown in the figure, the prepared tungsten oxide is granular, with a particle size between 100 and 200 nm, has a certain agglomeration behavior, and does not form a hierarchical structure. Its specific surface area BET is 8.48 m 2 / g.
[0105] Comparative Example 2
[0106] A method for preparing tungsten oxide comprises the following steps:
[0107] S1. Take 3L of ammonium tungstate solution for standby use; the concentration of the ammonium tungstate solution is 260g / L in terms of tungsten trioxide;
[0108] S2, taking hydrochloric acid for standby; the standby amount of the hydrochloric acid is 1.5 times the theoretical amount of hydrochloric acid required for preparing tungstic acid, and the concentration of the hydrochloric acid is 20wt%;
[0109] S3, adding the reserved ammonium tungstate solution dropwise to the reserved hydrochloric acid, stirring while dropping; stopping the dropping after a period of time, and stirring continuously during the stopping of the dropping; repeating the "dropping-stop dropping" method until the reserved ammonium tungstate solution is completely dropped to obtain tungstic acid; the stirring speed is 240r / min, the dropping speed of the ammonium tungstate solution is 100mL / min, the time of each dropping is 30min, the time of each stopping of dropping is 30min, and the number of repetitions of the "dropping-stop dropping" method is 1 time;
[0110] S4, filter and wash the tungstic acid, and then dry it; wash the tungstic acid with pure water, and the drying temperature is 120°C;
[0111] S5, calcining the dried tungstic acid at a temperature of 600°C for 1 hour to obtain tungsten oxide, such as Figure 7-8 As shown in the figure, the size of the prepared tungsten oxide is relatively uniform, all of which are large nanosheets with a thickness of less than 100nm. The nanosheets have a hierarchical structure, but the small and large particles are tightly attached, resulting in a reduction in pores, which will lead to a reduction in specific surface area. The specific surface area BET is 9.86m 2 / g.
[0112] Comparative Example 3
[0113] A method for preparing tungsten oxide comprises the following steps:
[0114] S1. Take 3L of ammonium tungstate solution for standby use; the concentration of the ammonium tungstate solution is 260g / L in terms of tungsten trioxide;
[0115] S2, taking hydrochloric acid for standby; the standby amount of the hydrochloric acid is 1.5 times the theoretical amount of hydrochloric acid required for preparing tungstic acid, and the concentration of the hydrochloric acid is 24wt%;
[0116] S3, dropwise add the reserved ammonium tungstate solution into the reserved hydrochloric acid, stirring while dropping until the reserved ammonium tungstate solution is completely dropped, and then stirring for 1h to obtain tungstic acid; the stirring speed is 120r / min, and the dropping speed of the ammonium tungstate solution is 100mL / min;
[0117] S4, filter and wash the tungstic acid, and then dry it; wash the tungstic acid with pure water, and the drying temperature is 120°C;
[0118] S5, calcining the dried tungstic acid at a temperature of 600°C for 1 hour to obtain tungsten oxide nanosheets, such as Figure 9-10 As shown in the figure, the size of the prepared tungsten oxide nanosheets is relatively uniform, all of which are relatively large nanosheets with a thickness of less than 100 nm. The nanosheets have not built a hierarchical structure and have agglomeration phenomenon. The specific surface area BET is 8.30 m2 / g.
[0119] Comparative Example 4
[0120] A method for preparing tungsten oxide comprises the following steps:
[0121] S1. Take 3L of ammonium tungstate solution for standby use; the concentration of the ammonium tungstate solution is 260g / L in terms of tungsten trioxide;
[0122] S2, taking hydrochloric acid for standby; the standby amount of the hydrochloric acid is 1.5 times the theoretical amount of hydrochloric acid required for preparing tungstic acid, and the concentration of the hydrochloric acid is 32wt%;
[0123] S3, drop the reserved ammonium tungstate solution into the reserved hydrochloric acid, and stir while dropping; stop dropping after a period of time, and continue stirring during the period of stopping dropping; repeat the "dropping-stop dropping" method until the reserved ammonium tungstate solution is completely dropped to obtain tungstic acid; the stirring speed is 200r / min, the dropping speed of the ammonium tungstate solution is 100mL / min, the time of each dropping is 15min, the time of each stopping dropping is 15min, and the number of repetitions of the "dropping-stop dropping" method is 2 times;
[0124] S4, filter and wash the tungstic acid, and then dry it; wash the tungstic acid with pure water, and the drying temperature is 120°C;
[0125] S5, calcining the dried tungstic acid at a temperature of 600°C for 1 hour to obtain tungsten oxide nanosheets, such as Figure 11-12 As shown in the figure, the prepared tungsten oxide nanosheets are all thick uniform sheets with a thickness of less than 100 nm, and no hierarchical structure is constructed. The BET value is 10.62m 2 / g.
[0126] Comparative Example 5
[0127] A method for preparing tungsten oxide comprises the following steps:
[0128] S1. Take 3L of ammonium tungstate solution for standby use; the concentration of the ammonium tungstate solution is 260g / L in terms of tungsten trioxide;
[0129] S2, taking hydrochloric acid for standby; the standby amount of the hydrochloric acid is 1.4 times the theoretical amount of hydrochloric acid required for preparing tungstic acid, and the concentration of the hydrochloric acid is 18wt%;
[0130] S3, dropwise add the reserved ammonium tungstate solution into the reserved hydrochloric acid, stir while dropping, until the reserved ammonium tungstate solution is completely dropped, and then stir for 1h to obtain tungstic acid; the stirring speed is 200r / min, and the dropping speed of the ammonium tungstate solution is 50mL / min;
[0131] S4, filter and wash the tungstic acid, and then dry it; wash the tungstic acid with pure water, and the drying temperature is 120°C;
[0132] S5, calcining the dried tungstic acid at a temperature of 800°C for 3 hours to obtain tungsten oxide nanosheets, such as Figure 13-14 As shown in Figure 2, the prepared nano-tungsten oxide is in the form of sheets with extremely uneven thickness, without forming a hierarchical structure, and with serious agglomeration. Its specific surface area is 6.72 m 2 / g.
[0133] Comparative Example 6
[0134] A method for preparing tungsten oxide comprises the following steps:
[0135] S1. Take 3L of ammonium tungstate solution for standby use; the concentration of the ammonium tungstate solution is 260g / L in terms of tungsten trioxide;
[0136] S2, taking hydrochloric acid for standby; the standby amount of the hydrochloric acid is 1.4 times the theoretical amount of hydrochloric acid required for preparing tungstic acid, and the concentration of the hydrochloric acid is 18wt%;
[0137] S3, adding the reserved ammonium tungstate solution dropwise to the reserved hydrochloric acid, stirring while dropping; stopping the dropping after a period of time, and stirring continuously during the stopping of the dropping; repeating the "dropping-stop dropping" method until the reserved ammonium tungstate solution is completely dropped to obtain tungstic acid; the stirring speed is 200r / min, the dropping speed of the ammonium tungstate solution is 50mL / min, the time of each dropping is 10min, the time of each stopping of dropping is 10min, and the number of repetitions of the "dropping-stop dropping" method is 6 times;
[0138] S4, filter and wash the tungstic acid, and then dry it; wash the tungstic acid with pure water, and the drying temperature is 120°C;
[0139] S5, calcining the dried tungstic acid at a temperature of 900°C for 3 hours to obtain tungsten oxide nanosheets, such as Fig.15 As shown in the figure, the prepared nano tungsten oxide has thicker flakes, and there are also tungsten oxide flakes stacked into blocks, without forming a hierarchical structure. Its specific surface area BET is 4.59m 2 / g.
[0140] Comparative Example 7
[0141] A method for preparing tungsten oxide comprises the following steps:
[0142] S1. Take 3L of ammonium tungstate solution for standby use; the concentration of the ammonium tungstate solution is 260g / L in terms of tungsten trioxide;
[0143] S2, taking hydrochloric acid for standby; the standby amount of the hydrochloric acid is 1.4 times the theoretical amount of hydrochloric acid required for preparing tungstic acid, and the concentration of the hydrochloric acid is 18wt%;
[0144] S3, adding the reserved ammonium tungstate solution dropwise to the reserved hydrochloric acid, stirring while dropping; stopping the dropping after a period of time, and stirring continuously during the stopping of the dropping; repeating the "dropping-stop dropping" method until the reserved ammonium tungstate solution is completely dropped to obtain tungstic acid; the stirring speed is 200r / min, the dropping speed of the ammonium tungstate solution is 200mL / min, the time of each dropping is 2.5min, the time of each stopping of dropping is 15min, and the number of repetitions of the "dropping-stop dropping" method is 6 times;
[0145] S4, filter and wash the tungstic acid, and then dry it; wash the tungstic acid with pure water, and the drying temperature is 120°C;
[0146] S5, calcining the dried tungstic acid at a temperature of 600°C for 1 hour to obtain tungsten oxide nanosheets, such as Fig.16 As shown in Figure 2, the prepared nano-tungsten oxide is in the form of thick sheets without forming a hierarchical structure. Its specific surface area is 5.02 m 2 / g.
[0147] It can be seen from the above embodiments and comparative examples that the tungsten oxide nanosheets of the present invention contain two sizes of non-uniform tungsten oxide sheets, the thickness of which is less than 100nm, and belong to nanostructured materials; compared with the prior art, the two sizes of tungsten oxide nanosheets construct a hierarchical structure at the micron level; the specific surface area BET is 17-21m 2 / g, tungsten oxide nanosheets are non-uniformly distributed at the microscopic level, and the non-uniform tungsten oxide nanosheets with hierarchical structures are coupled with each other, which can reduce agglomeration to a certain extent; tungsten oxide nanosheets are combined to construct a hierarchical structure at the micron level, which makes the material have abundant pores and can alleviate the volume change caused by the structural stress generated inside the material during the reaction process, which is beneficial to its application in the optoelectronic field, especially in the field of electrode materials.
[0148] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.
Claims
1. A method for preparing a non-uniform tungsten oxide nanosheet having a hierarchical structure, characterized in that: The steps include: S1. Take ammonium tungstate solution for later use; S2, take hydrochloric acid for use; S3, adding the reserved ammonium tungstate solution dropwise to the reserved hydrochloric acid, stirring while dropping; stopping the dropping after a period of time, and continuously stirring during the period of stopping the dropping; repeating the "dropping-stopping the dropping" method until all the reserved ammonium tungstate solution is dropped, to obtain tungstic acid; S4, filtering and washing the tungstic acid, and then drying; S5. calcining the dried tungstic acid to obtain non-uniform tungsten oxide nanosheets with a hierarchical structure.
2. The method for preparing the non-uniform tungsten oxide nanosheets with a hierarchical structure according to claim 1, characterized in that: In the step S1, the concentration of the ammonium tungstate solution is 250-300 g / L in terms of tungsten trioxide.
3. The method for preparing the non-uniform tungsten oxide nanosheets with a hierarchical structure according to claim 1, characterized in that: In step S2, the reserve amount of the hydrochloric acid is 1.3 to 1.7 times the theoretical amount of hydrochloric acid required for preparing tungstic acid, and the concentration of the hydrochloric acid is 16 to 24 wt%.
4. The method for preparing the non-uniform tungsten oxide nanosheets with a hierarchical structure according to claim 1, characterized in that: In step S3, the stirring speed is 180-260 r / min.
5. The method for preparing the non-uniform tungsten oxide nanosheets with a hierarchical structure according to claim 1, characterized in that: In the step S3, the dropping speed of the ammonium tungstate solution is 25-100 mL / min, and the time of each dropping is 5-15 min.
6. The method for preparing the non-uniform tungsten oxide nanosheets with a hierarchical structure according to claim 1, characterized in that: In the step S3, the time for stopping the dripping each time is 5 to 15 minutes.
7. The method for preparing the non-uniform tungsten oxide nanosheets with a hierarchical structure according to claim 1, characterized in that: In the step S4, tungstic acid is washed with pure water, and the drying temperature is 110-130°C.
8. The method for preparing the non-uniform tungsten oxide nanosheets with a hierarchical structure according to claim 1, characterized in that: In the step S5, the calcination temperature is 600-700° C., and the calcination time is 1-2 hours.
9. A non-uniform tungsten oxide nanosheet with a hierarchical structure, characterized in that: The tungsten oxide nanosheets are prepared by the method for preparing the non-uniform tungsten oxide nanosheets with a hierarchical structure according to any one of claims 1 to 8, wherein the tungsten oxide nanosheets are combined at the micron level to form a hierarchical structure, and the specific surface area is 17 to 21 m 2 / g.
10. Use of the non-uniform tungsten oxide nanosheets with a hierarchical structure as claimed in claim 9 in the field of optoelectronics.