A wO3 / tiO2 composite material, a preparation method and application thereof

Abstract

The application belongs to the technical field of nanometer materials, and particularly relates to a WO3 / TiO2 composite material, a preparation method and application thereof. The application provides a preparation method of a WO3 / TiO2 composite material, which comprises the following steps: mixing a tungsten precursor, water and a sulfuric acid solution to perform a first hydrothermal reaction to obtain a first product; mixing the first product, a titanium precursor and water to perform a second hydrothermal reaction to obtain a second product; and performing heat treatment on the second product in a hydrogen-containing atmosphere to obtain the WO3 / TiO2 composite material. The application first prepares a WO3 material by using a hydrothermal method, then loads TiO2 nanoparticles on the material, and then performs heat treatment to obtain the WO3 / TiO2 composite material. The WO3 / TiO2 composite material prepared by the application has high sensitivity to ammonia, low detection lower limit, good selectivity, and can be detected at room temperature, and has good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, specifically relating to a WO3 / TiO2 composite material, its preparation method, and its application. Background Technology

[0002] Ammonia is a colorless, water-soluble, toxic gas with a strong, pungent odor, and is one of the main air pollutants emitted by industry, agriculture, and automobiles. As an atmospheric and indoor pollutant, ammonia poses a serious threat to human health when exposed to it for extended periods.

[0003] Ammonia can also be used to assess the freshness of meat. During the spoilage process of fish and poultry, microorganisms and endogenous enzymes break down sulfhydryl-containing amino acids and proteins, releasing ammonia. Ammonia is also present in human exhaled breath and can serve as a typical biomarker for specific diseases, such as end-stage renal disease (ESRD), for rapid, non-invasive clinical diagnosis. The ammonia content in the exhaled breath of healthy individuals is approximately 0.4–1.8 ppm, while that in ESRD patients typically reaches levels above 14.7 ppm.

[0004] Tungsten oxide is an important n-type semiconductor functional material with a narrow bandgap, widely used in gas monitoring, photochromism, and photocatalysis due to its excellent crystal structure and good chemical stability. As a well-studied metal oxide semiconductor, tungsten oxide shows great promise in detecting gases such as ammonia, acetone, and H2S, and has been proven to be a promising gas-sensitive material. However, single-material tungsten oxide-based gas sensors still face many challenges, such as high operating temperature, poor selectivity, and low response time. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a WO3 / TiO2 composite material, its preparation method, and its application. The WO3 / TiO2 composite material prepared by this invention exhibits high selectivity and high response to ammonia at room temperature.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing a WO3 / TiO2 composite material, comprising the following steps:

[0008] A first hydrothermal reaction was carried out by mixing tungsten precursor, water and sulfuric acid solution to obtain the first product;

[0009] The first product, the titanium precursor, and water are mixed and subjected to a second hydrothermal reaction to obtain the second product.

[0010] The second product was heat-treated in a hydrogen-containing atmosphere to obtain the WO3 / TiO2 composite material.

[0011] Preferably, the tungsten precursor comprises tungstate and / or WCl6, wherein the tungstate comprises Na2WO4 or Na2WO4 hydrate.

[0012] Preferably, the temperature of the first hydrothermal reaction is 150-180°C and the time is 15-18 hours.

[0013] Preferably, the titanium precursor includes one or more of tetrabutyl titanate, titanium isopropoxide, and TiCl4.

[0014] Preferably, the molar ratio of the first product to the titanium precursor is 2 to 10:1.

[0015] Preferably, the temperature of the second hydrothermal reaction is 120-150°C and the time is 10-15 hours.

[0016] Preferably, the heat treatment temperature is 90-110°C and the time is 3-5 hours.

[0017] Preferably, the hydrogen-containing atmosphere is a hydrogen-argon mixture, and the volume concentration of hydrogen in the hydrogen-argon mixture is 3-5%.

[0018] The present invention also provides a WO3 / TiO2 composite material obtained by the preparation method described above, comprising WO3 nanoblocks and TiO2 nanoparticles loaded on the surface of the WO3 nanoblocks.

[0019] The present invention also provides the application of the WO3 / TiO2 composite material described in the above technical solution in ammonia detection.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention provides a method for preparing a WO3 / TiO2 composite material, comprising the following steps: mixing a tungsten precursor, water, and sulfuric acid solution to perform a first hydrothermal reaction to obtain a first product; mixing the first product, a titanium precursor, and water to perform a second hydrothermal reaction to obtain a second product; and heat-treating the second product in a hydrogen-containing atmosphere to obtain the WO3 / TiO2 composite material. This invention first prepares WO3 material using a hydrothermal method, then loads TiO2 nanoparticles onto this material, and then performs heat treatment to obtain the WO3 / TiO2 composite material. Compared to pure WO3, WO3... 3 / Due to the difference in Fermi levels between different materials, the TiO2 composite material facilitates electron-hole exchange. Simultaneously, the composite material increases the specific surface area, raises the baseline resistivity by constructing heterojunctions, and increases the change in resistance after contact with gas, thereby improving the response level. Heat treatment increases surface defects and active sites, as well as the contact area with the target gas, effectively enhancing the gas-sensing performance of the tungsten oxide-based material. Compared to pure WO3, the WO3 / TiO2 composite material prepared in this invention has a lower average porosity and a lower kinetic diameter of ammonia molecules, approximately 0.36–0.38 nm. The smaller pore size facilitates ammonia adsorption, significantly improving the sensitivity to ammonia, exhibiting a lower detection limit and better selectivity. Furthermore, it can be detected at room temperature, showing promising application prospects.

[0022] This invention uses a secondary hydrothermal method to prepare WO3 / TiO2 composite materials. The method is simple, low-cost, and has the potential to achieve mass production. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 The XRD pattern of the WO3 / TiO2 nanomaterials prepared in Example 3;

[0025] Figure 2 The real-time response curves of the WO3 / TiO2 composite material prepared in Example 3 to different concentrations of ammonia at room temperature are shown.

[0026] Figure 3 The results show the comparison of the response values ​​of the WO3 / TiO2 composite gas-sensitive material prepared in Example 3 to 50 ppm of different types of gases at room temperature.

[0027] Figure 4 SEM images of the materials prepared in Examples 1-4;

[0028] Figure 5 This is a SEM image of the material prepared in Example 5. Detailed Implementation

[0029] This invention provides a method for preparing a WO3 / TiO2 composite material, comprising the following steps:

[0030] A first hydrothermal reaction was carried out by mixing tungsten precursor, water and sulfuric acid solution to obtain the first product;

[0031] The first product, the titanium precursor, and water are mixed and subjected to a second hydrothermal reaction to obtain the second product.

[0032] The second product was heat-treated in a hydrogen-containing atmosphere to obtain the WO3 / TiO2 composite material.

[0033] Unless otherwise specified, all materials and equipment used in this invention are commercially available products in the field.

[0034] In this invention, a first hydrothermal reaction is carried out by mixing a tungsten precursor, water, and sulfuric acid solution to obtain a first product.

[0035] In this invention, the preferred method for mixing the tungsten precursor, water, and sulfuric acid solution is to first mix the tungsten precursor and water to obtain a tungsten precursor solution, and then mix it with the sulfuric acid solution.

[0036] In this invention, the tungsten precursor preferably comprises tungstate and / or WCl6, wherein the tungstate preferably comprises Na2WO4 or Na2WO4 hydrate, and the Na2WO4 hydrate is preferably Na2WO4·2H2O.

[0037] In this invention, the concentration of the tungsten precursor solution is preferably 0.1 to 0.17 mol / L, more preferably 0.1 to 0.12 mol / L.

[0038] In this invention, the concentration of the sulfuric acid solution is preferably 2 mol / L, and the volume ratio of the sulfuric acid solution to the tungsten precursor solution is preferably 30-40:30.

[0039] In this invention, the method of mixing the tungsten precursor, water and sulfuric acid solution is preferably by stirring, with the stirring speed preferably being 900 r / min and the stirring time preferably being 0.5 h; the stirring can ensure that the reactants are fully mixed and ensure the consistency of the reaction results.

[0040] In this invention, the temperature of the first hydrothermal reaction is preferably 150–180°C, more preferably 160–170°C, and the time is preferably 15–18 h, more preferably 16–17 h. During the first hydrothermal reaction, concentrated sulfuric acid and sodium tungstate react to generate WO3 and sodium sulfate, and the first product is WO3.

[0041] In this invention, the first hydrothermal reaction is preferably carried out in a polytetrafluoroethylene reactor, preferably under constant temperature conditions, and the filling rate of the polytetrafluoroethylene reactor is preferably 50-80%, more preferably 60-70%.

[0042] In this invention, the process after the first hydrothermal reaction preferably includes cooling, solid-liquid separation, washing the obtained solid, and drying.

[0043] In this invention, the temperature after cooling is preferably room temperature, the solid-liquid separation method is preferably centrifugation, the centrifugation speed is preferably 12000 r / min, and the centrifugation time is preferably 5 to 10 min.

[0044] In this invention, the washing preferably includes ethanol washing and water washing, and the ethanol washing and water washing are preferably performed alternately, and the number of alternations is preferably 3 times.

[0045] In this invention, the drying temperature is preferably 60°C, and the drying time is preferably 10-15 hours, more preferably 12 hours.

[0046] After obtaining the first product, the present invention mixes the first product, the titanium precursor and water to carry out a second hydrothermal reaction to obtain the second product.

[0047] In this invention, the titanium precursor preferably comprises one or more of tetrabutyl titanate, titanium isopropoxide, and TiCl4, more preferably tetrabutyl titanate. The titanium precursor of this invention does not exhibit large-area aggregation of TiO2 (when using tetraisopropyl titanate, TiO2 exhibits large-area aggregation). This invention uses tetrabutyl titanate as the titanium source to obtain anatase TiO2 and uses TiCl4 to obtain rutile phase titanium oxide.

[0048] In this invention, the molar ratio of the first product to the titanium precursor is preferably 2 to 10:1, more preferably 10:3.

[0049] In this invention, the titanium precursor is preferably used in the form of a titanium precursor alcohol solution, more preferably a titanium precursor ethylene glycol solution or a titanium precursor ethanol solution. The volume ratio of tetrabutyl titanate to ethylene glycol in the titanium precursor ethylene glycol solution is preferably 0.03-0.2:10-20 (30-200 μL:10-20 mL), more preferably 0.034-0.17:10-20, and even more preferably 0.12:10-20.

[0050] In this invention, when the titanium precursor is preferably tetrabutyl titanate, the ratio of the first product to the titanium precursor is preferably 0.232g:30-200μL, more preferably 0.232g:34-170μL, and even more preferably 0.232g:102μL.

[0051] In this invention, the volume ratio of the titanium precursor alcohol solution to water is preferably 10-20:60.

[0052] In this invention, the method of mixing the first product, the titanium precursor and water is preferably by stirring, the stirring speed is preferably 900 r / min and the stirring time is preferably 0.5 h; the stirring can make the reactants fully mixed and ensure the consistency of the reaction results.

[0053] In this invention, the temperature of the second hydrothermal reaction is preferably 120–150°C, more preferably 130–140°C, and the time is preferably 10–15 h, more preferably 12 h. During the second hydrothermal reaction, the alcohol and the titanium precursor react to generate TiO2.

[0054] In this invention, the second hydrothermal reaction is preferably carried out in a polytetrafluoroethylene reactor, preferably under constant temperature conditions, and the filling rate of the polytetrafluoroethylene reactor is preferably 50-80%, more preferably 80%.

[0055] In this invention, the second hydrothermal reaction preferably further includes cooling, solid-liquid separation, washing the obtained solid, and drying.

[0056] In this invention, the temperature after cooling is preferably room temperature, the solid-liquid separation method is preferably centrifugation, the centrifugation speed is preferably 12000 r / min, and the centrifugation time is preferably 5 to 10 min.

[0057] In this invention, the washing preferably includes ethanol washing and water washing, and the ethanol washing and water washing are preferably performed alternately, and the number of alternations is preferably 3 times.

[0058] In this invention, the drying temperature is preferably 60°C, and the drying time is preferably 10-15 hours, more preferably 12 hours.

[0059] After obtaining the second product, the present invention heat-treats the second product in a hydrogen-containing atmosphere to obtain the WO3 / TiO2 composite material.

[0060] In this invention, the hydrogen-containing atmosphere is preferably a hydrogen-argon mixture, and the volume concentration of hydrogen in the hydrogen-argon mixture is preferably 3-5%. The hydrogen content in the hydrogen-containing atmosphere of this invention is relatively low, and in a specific embodiment of this invention, the gas flow is stopped after 10 minutes. Heat treatment in the hydrogen-containing atmosphere of this invention can increase the oxygen vacancy content of the material, and oxygen vacancies are beneficial for the adsorption of gas molecules.

[0061] In this invention, the heat treatment temperature is preferably 90-110°C, more preferably 100°C, and the time is preferably 3-5 hours. The heat treatment conditions described in this invention can improve the crystal structure, defect structure, and properties of the material, thereby improving the stability and gas-sensitive properties of the nanomaterial.

[0062] The present invention also provides a WO3 / TiO2 composite material obtained by the preparation method described above, comprising WO3 nanoblocks and TiO2 nanoparticles loaded on the surface of the WO3 nanoblocks.

[0063] In this invention, the WO3 / TiO2 composite material is a blocky structure in which TiO2 nanoparticles are coated with WO3 nanoblocks.

[0064] In this invention, the size of the WO3 nanoblocks is preferably 80-120 nm, and the particle size of the TiO2 nanoparticles is preferably 10-30 nm.

[0065] In this invention, the loading of the TiO2 nanoparticles is preferably 10-50 at% of the WO3 nanoblocks, more preferably 30 at%.

[0066] The present invention also provides the application of the WO3 / TiO2 composite material described in the above technical solution in ammonia detection.

[0067] In this invention, the ammonia detection uses a gas sensor, and the gas-sensitive electrode of the gas sensor is provided with a gas-sensitive coating. The material of the gas-sensitive coating includes the WO3 / TiO2 composite material described in the above technical solution.

[0068] The WO3 / TiO2 composite material of the present invention exhibits high sensitivity at room temperature and good selectivity for ammonia.

[0069] To further illustrate the present invention, the WO3 / TiO2 composite material, its preparation method, and its application provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0070] Example 1

[0071] (1) Weigh 1g of Na2WO4·2H2O solid particles and dissolve them in 30mL of deionized water, stirring until homogeneous. Add 30mL of 2mol / L sulfuric acid to the above solution and stir at 900r / min for 0.5h;

[0072] (2) The mixed solution obtained in step (1) was transferred to a polytetrafluoroethylene (PTFE) reactor, with the reactor filling rate maintained at 60%. The reactor was kept at a constant temperature of 150℃ for 18 hours. After the product temperature dropped to room temperature, it was centrifuged at a rate of 12000 r / min for 5 minutes, and then the precipitate was washed three times alternately with ethanol and deionized water. The centrifuged precipitate was dried in a 60℃ forced-air drying oven for 12 hours to obtain WO3 material.

[0073] Example 2

[0074] (1) Weigh 1g of Na2WO4·2H2O solid particles and dissolve them in 30mL of deionized water, stirring until homogeneous. Add 30mL of 2mol / L sulfuric acid to the above solution and stir at 900r / min for 0.5h;

[0075] (2) Transfer the mixed solution obtained in step (1) to a polytetrafluoroethylene reactor, maintaining a reactor filling rate of 60%. Keep the reactor at a constant temperature of 150℃ for 18 hours. After the product temperature drops to room temperature, centrifuge at 12000 r / min for 5 minutes, then wash the precipitate three times alternately with ethanol and deionized water. Dry the centrifuged precipitate in a 60℃ forced-air drying oven for 12 hours.

[0076] (3) Weigh 0.232 g of the above precipitate and dissolve 34 μL of tetrabutyl titanate in 20 mL of ethylene glycol, stirring until homogeneous. Add 60 mL of deionized water to the above raw materials and stir at 900 r / min for 0.5 h;

[0077] (4) Transfer the mixed solution obtained in step (3) to a polytetrafluoroethylene reactor, maintaining the reactor filling rate at 80%. Keep the reactor at a constant temperature of 120℃ for 12 hours. After the product temperature drops to room temperature, centrifuge at 12000 r / min for 5 minutes, then wash the precipitate three times alternately with ethanol and deionized water. Dry the centrifuged precipitate in a 60℃ forced-air drying oven for 12 hours.

[0078] (5) The product was placed in a hydrogen-argon mixture with a hydrogen volume ratio of 3% and heat-treated at 100°C for 3 hours to obtain a WO3 / TiO2 composite material that can be used for ammonia detection at room temperature.

[0079] Example 3

[0080] (1) Weigh 1g of Na2WO4·2H2O solid particles and dissolve them in 30mL of deionized water, stirring until homogeneous. Add 30mL of 2mol / L sulfuric acid to the above solution and stir at 900r / min for 0.5h;

[0081] (2) Transfer the mixed solution obtained in step (1) to a polytetrafluoroethylene reactor, maintaining a reactor filling rate of 60%. Keep the reactor at a constant temperature of 180℃ for 15 hours. After the product temperature drops to room temperature, centrifuge at 12000 r / min for 5 minutes, then wash the precipitate three times alternately with ethanol and deionized water. Dry the centrifuged precipitate in a 60℃ forced-air drying oven for 12 hours.

[0082] (3) Weigh 0.232 g of the above precipitate, and dissolve 102 μL of tetrabutyl titanate in 20 mL of ethylene glycol, stirring until homogeneous. Add 60 mL of deionized water to the above raw materials and stir at 900 r / min for 0.5 h;

[0083] (4) Transfer the mixed solution obtained in step (3) to a polytetrafluoroethylene reactor, maintaining a reactor filling rate of 80%. Keep the reactor at a constant temperature of 140℃ for 12 hours. After the product temperature drops to room temperature, centrifuge at 12000 r / min for 5 minutes, then wash the precipitate three times alternately with ethanol and deionized water. Dry the centrifuged precipitate in a 60℃ forced-air drying oven for 12 hours.

[0084] (5) The product was placed in a hydrogen-argon mixture with a hydrogen volume ratio of 3% and heat-treated at 100°C for 3 hours to obtain a WO3 / TiO2 composite material that can be used for ammonia detection at room temperature.

[0085] Example 4

[0086] (1) Weigh 1.2g of Na2WO4·2H2O solid particles and dissolve them in 36mL of deionized water, stirring until homogeneous. Add 36mL of 2mol / L sulfuric acid to the above solution and stir at 900r / min for 0.5h;

[0087] (2) Transfer the mixed solution obtained in step (1) to a polytetrafluoroethylene reactor, maintaining a reactor filling rate of 70%. Keep the reactor at a constant temperature of 150℃ for 18 hours. After the product temperature drops to room temperature, centrifuge at 12000 r / min for 5 minutes, then wash the precipitate three times alternately with ethanol and deionized water. Dry the centrifuged precipitate in a 60℃ forced-air drying oven for 12 hours.

[0088] (3) Weigh 0.232 g of the above precipitate, and dissolve 170 μL of tetrabutyl titanate in 20 mL of ethylene glycol, stirring until homogeneous. Add 60 mL of deionized water to the above raw materials and stir at 900 r / min for 0.5 h;

[0089] (4) Transfer the mixed solution obtained in step (3) to a polytetrafluoroethylene reactor, maintaining a reactor filling rate of 80%. Keep the reactor at a constant temperature of 150℃ for 15 hours. After the product temperature drops to room temperature, centrifuge at 12000 r / min for 5 minutes, then wash the precipitate three times alternately with ethanol and deionized water. Dry the centrifuged precipitate in a 60℃ forced-air drying oven for 12 hours.

[0090] (5) The product was placed in a hydrogen-argon mixture with a hydrogen volume ratio of 3% and heat-treated at 100°C for 3 hours to obtain a WO3 / TiO2 composite material that can be used for ammonia detection at room temperature.

[0091] Figure 1The image shows the XRD pattern of the WO3 / TiO2 nanomaterials prepared in Example 3. The diffraction pattern reveals diffraction peaks at 23.122°, 23.582°, 24.379°, 26.590°, 28.620°, 28.942°, 33.270°, and 34.170°, corresponding to the (002), (020), (200), (120), and (-) peaks of WO3, respectively. The material sample exhibits diffraction peaks at 25.211°, 36.745°, 53.534° and 54.861°, corresponding to the (101), (103), (105) and (211) crystal planes of anatase TiO2, respectively (JCPDS, No. 71-1168).

[0092] Figure 2 The figure shows the real-time response curves of the WO3 / TiO2 composite material prepared in Example 3 to different concentrations of ammonia at room temperature. The numbers in the figure represent the ammonia concentration. The characteristic curves show that the response value of the composite material in 50 ppm ammonia is close to 100. The intercept of the response characteristic curve was obtained by linear fitting, and the theoretical detection threshold reached 0.5 ppm, which meets the current market demand for room temperature ammonia detection.

[0093] Figure 3 The results show a comparison of the response values ​​of the WO3 / TiO2 composite gas-sensitive material prepared in Example 3 to 50 ppm of different gases at room temperature. The results indicate that the composite material's response to ammonia is significantly higher than its response to other gases under the same room temperature conditions, demonstrating its high selectivity for ammonia. The response values ​​of the materials prepared in Examples 1-4 to 50 ppm of ammonia at room temperature are 6.37, 31.95, 92.28, and 49.50, respectively.

[0094] Figure 4 The images show SEM images of the materials prepared in Examples 1-4. The material prepared in Example 1 is a nanobulb structure, while the materials prepared in Examples 2-4 are bulk structures of nanoparticles coated with nanobulbs. The TiO2 loading can be observed to increase from low to high. The molar loadings of the materials prepared in Examples 1-4 are 0%, 10%, 30%, and 50% (atomic ratio of Ti to Wu relative to WO3), and their specific surface areas are 5.7644 m², respectively. 2 / g, 19.5627m 2 / g, 23.5641m 2 / g and 11.6382m 2 / g.

[0095] Example 5

[0096] The difference from Example 3 is that the 102 μL of tetrabutyl titanate in step (3) is replaced with 88 μL of tetraisopropyl titanate, and the other steps are the same.

[0097] Figure 5 The images shown are SEM images of the material prepared in Example 5 (the left and right images are at different magnifications, respectively). It can be seen that TiO2 exhibits large-area aggregation.

[0098] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on the present invention without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. An application of a WO3 / TiO2 composite material in ammonia detection, characterized in that, The preparation method of the WO3 / TiO2 composite material includes the following steps: A first hydrothermal reaction was carried out by mixing tungsten precursor, water and sulfuric acid solution to obtain the first product; The first product, titanium precursor, and water are mixed and subjected to a second hydrothermal reaction to obtain a second product; the molar ratio of the first product to the titanium precursor is 2~10:

1. The second product was heat-treated in a hydrogen-containing atmosphere to obtain the WO3 / TiO2 composite material; the heat treatment temperature was 90~110℃ and the time was 3~5h. The WO3 / TiO2 composite material includes WO3 nanoblocks and TiO2 nanoparticles loaded on the surface of the WO3 nanoblocks.

2. The application according to claim 1, characterized in that, The tungsten precursor includes tungstate and / or WCl6, wherein the tungstate includes Na2WO4 or Na2WO4 hydrate.

3. The application according to claim 1, characterized in that, The temperature of the first hydrothermal reaction is 150~180℃, and the time is 15~18h.

4. The application according to claim 1, characterized in that, The titanium precursor includes one or more of tetrabutyl titanate, titanium isopropoxide, and TiCl4.

5. The application according to claim 1, characterized in that, The temperature of the second hydrothermal reaction is 120~150℃, and the time is 10~15h.

6. The application according to claim 1, characterized in that, The hydrogen-containing atmosphere is a hydrogen-argon mixture, and the volume concentration of hydrogen in the hydrogen-argon mixture is 3-5%.

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